A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position.
146-538: In its simplest form, it consists of an outer case with mirrors at each end set parallel to each other at a 45° angle. This form of periscope, with the addition of two simple lenses, served for observation purposes in the trenches during World War I . Military personnel also use periscopes in some gun turrets and in armoured vehicles . More complex periscopes using prisms or advanced fiber optics instead of mirrors and providing magnification operate on submarines and in various fields of science. The overall design of
292-481: A circular cylinder or of a parabolic cylinder . The most common structural material for mirrors is glass, due to its transparency, ease of fabrication, rigidity, hardness, and ability to take a smooth finish. The most common mirrors consist of a plate of transparent glass, with a thin reflective layer on the back (the side opposite to the incident and reflected light) backed by a coating that protects that layer against abrasion, tarnishing, and corrosion . The glass
438-511: A coalition force or part of a United Nations peacekeeping operation. Until the Wars of the Three Kingdoms , neither England or Scotland had had a standing army with professional officers and career corporals and sergeants. England relied on militia organised by local officials or private forces mobilised by the nobility, or on hired mercenaries from Europe. From the later Middle Ages until
584-795: A curved mirror may distort, magnify, or reduce the image in various ways, while keeping the lines, contrast , sharpness , colors, and other image properties intact. A mirror is commonly used for inspecting oneself, such as during personal grooming ; hence the old-fashioned name "looking glass". This use, which dates from prehistory, overlaps with uses in decoration and architecture . Mirrors are also used to view other items that are not directly visible because of obstructions; examples include rear-view mirrors in vehicles, security mirrors in or around buildings, and dentist's mirrors . Mirrors are also used in optical and scientific apparatus such as telescopes , lasers , cameras , periscopes , and industrial machinery. According to superstitions breaking
730-405: A mirror image or reflected image of objects in the environment, formed by light emitted or scattered by them and reflected by the mirror towards one's eyes. This effect gives the illusion that those objects are behind the mirror, or (sometimes) in front of it . When the surface is not flat, a mirror may behave like a reflecting lens . A plane mirror yields a real-looking undistorted image, while
876-432: A virtual image of whatever is in the opposite angle from the viewer, meaning that objects in the image appear to exist in a direct line of sight —behind the surface of the mirror—at an equal distance from their position in front of the mirror. Objects behind the observer, or between the observer and the mirror, are reflected back to the observer without any actual change in orientation; the light waves are simply reversed in
1022-779: A 21-year engagement, following which (should he survive so long) he was discharged as a Pensioner. Pensioners were sometimes still employed on garrison duties, as were younger soldiers no longer deemed fit for expeditionary service who were generally organised in invalid units or returned to the regimental depot for home service. The cost of paying pensioners, and the obligation the government was under to continue to employ invalids as well as soldiers deemed by their commanding officers as detriments to their units were motivations to change this system. The long period of engagement also discouraged many potential recruits. The long service enlistments were consequently replaced with short service enlistments, with undesirable soldiers not permitted to re-engage on
1168-562: A Catholic) during his brief controversial reign, off the throne and into exile. England then involved itself in the War of the Grand Alliance on the Continent, primarily to prevent a possible French Catholic monarch organizing invasion restoring the exiled James II (Queen Mary's father and still a Roman Catholic ). Later in 1689, William III to solidify his and Mary's hold on the monarchy, expanded
1314-569: A Parliamentary-funded army, commanded by Lord General Thomas Fairfax , which became known as the New Model Army (originally phrased "new-modelled Army"). While this proved to be a war-winning formula, the New Model Army, being organised and politically active, went on to dominate the politics of the Interregnum and by 1660 was widely disliked. The New Model Army was paid off and disbanded at
1460-456: A century, Venice retained the monopoly of the tin amalgam technique. Venetian mirrors in richly decorated frames served as luxury decorations for palaces throughout Europe, and were very expensive. For example, in the late seventeenth century, the Countess de Fiesque was reported to have traded an entire wheat farm for a mirror, considering it a bargain. However, by the end of that century the secret
1606-619: A combination of prisms to relay the image to the submariner. (Peral also developed a primitive gyroscope for submarine navigation and pioneered the ability to fire live torpedoes while submerged.) The invention of the collapsible periscope for use in submarine warfare is usually credited to Simon Lake in 1902. Lake called his device the "omniscope" or "skalomniscope". As of 2009 modern submarine periscopes incorporate lenses for magnification and function as telescopes . They typically employ prisms and total internal reflection instead of mirrors, because prisms, which do not require coatings on
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#17328553791901752-418: A concave parabolic mirror (whose surface is a part of a paraboloid of revolution) will reflect rays that are parallel to its axis into rays that pass through its focus . Conversely, a parabolic concave mirror will reflect any ray that comes from its focus towards a direction parallel to its axis. If a concave mirror surface is a part of a prolate ellipsoid , it will reflect any ray coming from one focus toward
1898-679: A deployment in Afghanistan as part of Operation Toral . Following an announcement by the US Government of the end of their operations in the Afghanistan, the Ministry of Defence announced in April 2021 that British forces would withdraw from the country by 11 September 2021. It was later reported that all UK troops would be out by early July. Following the collapse of the Afghan Army, and the completion of
2044-534: A device that can rotate to provide a wider field of view (or is fixed into an assembly that can), while an episcope is fixed into position. Periscopes may also be referred to by slang, e.g. "shufti-scope". An important development, the Gundlach rotary periscope , incorporated a rotating top with a selectable additional prism which reversed the view. This allowed a tank commander to obtain a 360-degree field of view without moving his seat, including rear vision by engaging
2190-426: A different image in the same mirror. Thus, the images observed in a mirror depend upon the angle of the mirror with respect to the eye. The angle between the object and the observer is always twice the angle between the eye and the normal, or the direction perpendicular to the surface. This allows animals with binocular vision to see the reflected image with depth perception and in three dimensions. The mirror forms
2336-401: A direction perpendicular to the mirror. However, when viewer is facing the object and the mirror is at an angle between them, the image appears inverted 180° along the direction of the angle. Objects viewed in a (plane) mirror will appear laterally inverted (e.g., if one raises one's right hand, the image's left hand will appear to go up in the mirror), but not vertically inverted (in the image
2482-776: A good mirror are a surface with a very high degree of flatness (preferably but not necessarily with high reflectivity ), and a surface roughness smaller than the wavelength of the light. The earliest manufactured mirrors were pieces of polished stone such as obsidian , a naturally occurring volcanic glass . Examples of obsidian mirrors found at Çatalhöyük in Anatolia (modern-day Turkey) have been dated to around 6000 BCE. Mirrors of polished copper were crafted in Mesopotamia from 4000 BCE, and in ancient Egypt from around 3000 BCE. Polished stone mirrors from Central and South America date from around 2000 BCE onwards. By
2628-585: A large reserve of recently discharged soldiers, ready to be recalled on the outbreak of war to immediately bring the small peacetime regular army up to strength), the Regular Reserve of the British Army was originally created in 1859 by Secretary of State for War Sidney Herbert , and re-organised under the Reserve Force Act 1867 . Prior to this, a soldier was generally enlisted into the British Army for
2774-415: A layer of paint applied over it. Mirrors for optical instruments often have the metal layer on the front face, so that the light does not have to cross the glass twice. In these mirrors, the metal may be protected by a thin transparent coating of a non-metallic ( dielectric ) material. The first metallic mirror to be enhanced with a dielectric coating of silicon dioxide was created by Hass in 1937. In 1939 at
2920-409: A left-hand glove into a right-hand glove or vice versa). When a person raises their left hand, the actual left hand raises in the mirror, but gives the illusion of a right hand raising because the imaginary person in the mirror is literally inside-out, hand and all. If the person stands side-on to a mirror, the mirror really does reverse left and right hands, that is, objects that are physically closer to
3066-572: A member of parliament and future Lord Protector) from serving as officers in the Parliamentary armies. This created a distinction between the civilians in Parliament, who tended to be Presbyterian and conciliatory to the Royalists ("Cavaliers") in nature, and a corps of professional officers, who tended to be Independent ( Congregational ) in theology. The second action was legislation for the creation of
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#17328553791903212-773: A mirror is said to bring seven years of bad luck . The terms "mirror" and "reflector" can be used for objects that reflect any other types of waves. An acoustic mirror reflects sound waves. Objects such as walls, ceilings, or natural rock-formations may produce echos , and this tendency often becomes a problem in acoustical engineering when designing houses, auditoriums, or recording studios. Acoustic mirrors may be used for applications such as parabolic microphones , atmospheric studies, sonar , and seafloor mapping . An atomic mirror reflects matter waves and can be used for atomic interferometry and atomic holography . The first mirrors used by humans were most likely pools of still water, or shiny stones. The requirements for making
3358-565: A multinational armoured battlegroup in Estonia under Operation Cabrit and contributes troops to another military battle group in Poland . As part of the NATO plans, Britain has committed a full mechanized infantry brigade to be on a high state of readiness to defend Estonia. Between 2015 and 2022, the British Army deployed Short Term Training Teams (STTTs) to Ukraine under Operation Orbital to help train
3504-501: A narrower field of view and higher magnification. In World War II and earlier submarines it was the only means of gathering target data to accurately fire a torpedo, since sonar was not yet sufficiently advanced for this purpose (ranging with sonar required emission of an acoustic "ping" that gave away the location of the submarine) and most torpedoes were unguided. Twenty-first-century submarines do not necessarily have periscopes. The United States Navy's Virginia -class submarines and
3650-402: A person's head still appears above their body). However, a mirror does not actually "swap" left and right any more than it swaps top and bottom. A mirror swaps front and back. To be precise, it reverses the object in the direction perpendicular to the mirror surface (the normal), turning the three dimensional image inside out (the way a glove stripped off the hand can be turned inside out, turning
3796-413: A point are usually made in the shape of a paraboloid of revolution instead; they are used in telescopes (from radio waves to X-rays), in antennas to communicate with broadcast satellites , and in solar furnaces . A segmented mirror , consisting of multiple flat or curved mirrors, properly placed and oriented, may be used instead. Mirrors that are intended to concentrate sunlight onto a long pipe may be
3942-472: A protective transparent coating is added on top of the reflecting layer, to protect it against abrasion, tarnishing, and corrosion, or to absorb certain wavelengths. Thin flexible plastic mirrors are sometimes used for safety, since they cannot shatter or produce sharp flakes. Their flatness is achieved by stretching them on a rigid frame. These usually consist of a layer of evaporated aluminium between two thin layers of transparent plastic. In common mirrors,
4088-832: A safe distance by aiding the Ottoman Empire ). Like the English Army , the British Army fought the kingdoms of Spain, France (including the First French Empire ) and the Netherlands ( Dutch Republic ) for supremacy in North America and the West Indies . With native and provincial and colonial assistance, the Army conquered New France in the French and Indian War (North American theatre) of
4234-586: A small fraction of the rays are reflected. In flying relativistic mirrors conceived for X-ray lasers , the reflecting surface is a spherical shockwave (wake wave) created in a low-density plasma by a very intense laser-pulse, and moving at an extremely high velocity. A phase-conjugating mirror uses nonlinear optics to reverse the phase difference between incident beams. Such mirrors may be used, for example, for coherent beam combination. The useful applications are self-guiding of laser beams and correction of atmospheric distortions in imaging systems. When
4380-408: A sufficiently narrow beam of light is reflected at a point of a surface, the surface's normal direction n → {\displaystyle {\vec {n}}} will be the bisector of the angle formed by the two beams at that point. That is, the direction vector u → {\displaystyle {\vec {u}}} towards the incident beams's source,
4526-505: A target strength of 82,000, and just over 30,000 Army Reservists , with a target strength of 30,000. All former Regular Army personnel may also be recalled to duty in exceptional circumstances during the 6-year period following completion of their Regular service, which creates an additional force known as the Regular Reserve . The table below illustrates British Army personnel figures from 1710 to 2024. The British Army's basic weapon
Periscope - Misplaced Pages Continue
4672-466: A targeting, or commander's, periscope. Navies originally mounted these periscopes in the conning tower , one forward of the other in the narrow hulls of diesel-electric submarines. In the much wider hulls of recent US Navy submarines the two operate side-by-side. The observation scope, used to scan the sea surface and sky, typically had a wide field of view and no magnification or low-power magnification. The targeting or "attack" periscope, by comparison, had
4818-419: A variety of materials for thousands of years, like stone, metals, and glass. In modern mirrors, metals like silver or aluminium are often used due to their high reflectivity , applied as a thin coating on glass because of its naturally smooth and very hard surface. A mirror is a wave reflector. Light consists of waves, and when light waves reflect from the flat surface of a mirror, those waves retain
4964-641: A volunteer army and threatened to emulate the American colonists if their conditions were not met. Learning from their experience in America, the British government sought a political solution. The British Army fought Irish rebels—Protestant and Catholic—primarily in Ulster and Leinster ( Wolfe Tone's United Irishmen ) in the 1798 rebellion . In addition to battling the armies of other European empires (and its former colonies,
5110-793: A war against the Prussian -led German Empire and the Austro-Hungarian Empire ). When the First World War broke out in August 1914 the British Army sent the British Expeditionary Force (BEF), consisting mainly of regular army troops, to France and Belgium . The fighting bogged down into static trench warfare for the remainder of the war. In 1915 the army created the Mediterranean Expeditionary Force to invade
5256-507: Is a dichroic mirror that efficiently reflects the entire visible light spectrum while transmitting infrared wavelengths. A hot mirror is the opposite: it reflects infrared light while transmitting visible light. Dichroic mirrors are often used as filters to remove undesired components of the light in cameras and measuring instruments. In X-ray telescopes , the X-rays reflect off a highly precise metal surface at almost grazing angles, and only
5402-625: Is based on that of the earlier English army. Although technically the Scots Royal Regiment of Foot was raised in 1633 and is the oldest Regiment of the Line, Scottish and Irish regiments were only allowed to take a rank in the English army on the date of their arrival in England (or the date when they were first placed on the English establishment). In 1694, a board of general officers was convened to decide
5548-443: Is broken. Lettering or decorative designs may be printed on the front face of the glass, or formed on the reflective layer. The front surface may have an anti-reflection coating . Mirrors which are reflective on the front surface (the same side of the incident and reflected light) may be made of any rigid material. The supporting material does not necessarily need to be transparent, but telescope mirrors often use glass anyway. Often
5694-403: Is no archeological evidence of glass mirrors before the third century. These early glass mirrors were made by blowing a glass bubble, and then cutting off a small circular section from 10 to 20 cm in diameter. Their surface was either concave or convex, and imperfections tended to distort the image. Lead-coated mirrors were very thin to prevent cracking by the heat of the molten metal. Due to
5840-692: Is provided by L16 81mm mortars . Sniper rifles include the L118A1 7.62 mm, L115A3 and the AW50F , all manufactured by Accuracy International . The British Army utilises the Glock 17 as its side arm. Anti tank guided weapons include the Javelin , the medium range anti-tank guided weapon replacement for Milan , with overfly and direct attack modes of operation, and the NLAW . The Next-generation Light Anti-tank Weapon ( NLAW )
5986-505: Is the 5.56 mm L85A2 or L85A3 assault rifle, with some specialist personnel using the L22A2 carbine variant (pilots and some tank crew). The weapon was traditionally equipped with either iron sights or an optical SUSAT , although other optical sights have been subsequently purchased to supplement these. The weapon can be enhanced further utilising the Picatinny rail with attachments such as
Periscope - Misplaced Pages Continue
6132-576: Is the first, non-expert, short-range, anti-tank missile that rapidly knocks out any main battle tank in just one shot by striking it from above. The army's main battle tank is the Challenger 2 , which is being upgraded to Challenger 3 . It is supported by the Warrior tracked armoured vehicle as the primary infantry fighting vehicle , (which will soon be replaced by the Boxer 8x8 armoured fighting vehicle ) and
6278-643: Is the official list of which bodies of the British Military (not to be confused with naval ) Forces were to be considered Corps of the British Army for the purposes of the Army Act , the Reserve Forces Act, 1882, and the Territorial and Reserve Forces Act, 1907, had not been updated since 1926 (Army Order 49 of 1926), although amendments had been made up to and including Army Order 67 of 1950. A new Corps Warrant
6424-408: Is usually soda-lime glass, but lead glass may be used for decorative effects, and other transparent materials may be used for specific applications. A plate of transparent plastic may be used instead of glass, for lighter weight or impact resistance. Alternatively, a flexible transparent plastic film may be bonded to the front and/or back surface of the mirror, to prevent injuries in case the mirror
6570-707: The American Revolutionary War , the Napoleonic Wars , the Crimean War and the First and Second World Wars . Britain's victories in most of these decisive wars allowed it to influence world events and establish itself as one of the world's leading military and economic powers. Since the end of the Cold War , the British Army has been deployed to a number of conflict zones, often as part of an expeditionary force ,
6716-526: The Americas , Africa , Asia , India and Australasia . British soldiers captured strategically important sites and territories, with the army involved in wars to secure the empire's borders, internal safety and support friendly governments and princes. Among these actions were the French and Indian War / Seven Years' War, the American Revolutionary War , the Napoleonic Wars , the First and Second Opium Wars ,
6862-603: The Anglo-Irish War . The increasing demands of imperial expansion and the inadequacy and inefficiency of the underfunded British Army, Militia , Ordnance Military Corps, Yeomanry and Volunteer Force after the Napoleonic Wars led to series of reforms following the failures of the Crimean War . Inspired by the successes of the Prussian Army (which relied on short-term conscription of all eligible young men to maintain
7008-668: The Armed Forces of Ukraine against further Russian aggression. This operation was succeeded by Operation Interflex in July 2022. The British Army has been a volunteer force since national service ended during the 1960s. Since the creation of the part-time, reserve Territorial Force in 1908 (renamed the Army Reserve in 2014), the full-time British Army has been known as the Regular Army. In July 2020 there were just over 78,800 Regulars, with
7154-572: The Avro Vulcan and Handley Page Victor and the Nimrod MR1 as the "on top sight". Various US bomber aircraft such as the B-52 used sextant periscopes for celestial navigation before the introduction of GPS . This also allowed the aircrew to navigate without the use of an astrodome in the fuselage. An emergency periscope was used on all Boeing 737 models manufactured before 1997 found under "Seat D" behind
7300-951: The Boxer Rebellion , the New Zealand Wars , the Australian frontier wars , the Sepoy Rebellion of 1857 , the first and second Boer Wars , the Fenian raids , the Irish War of Independence , interventions in Afghanistan (intended to maintain a buffer state between British India and the Russian Empire ) and the Crimean War (to keep the Russian Empire to the north on the Black Sea at
7446-781: The British Army . Members of the British Army swear allegiance to the monarch as their commander-in-chief , since both the English Bill of Rights of 1689 and Scottish Claim of Right Act 1689 require parliamentary consent for the Crown to maintain a peacetime standing army . The army is administered by the Ministry of Defence and commanded by the Chief of the General Staff . At its inception, being composed primarily of cavalry and infantry,
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#17328553791907592-519: The Bronze Age most cultures were using mirrors made from polished discs of bronze , copper , silver , or other metals. The people of Kerma in Nubia were skilled in the manufacturing of mirrors. Remains of their bronze kilns have been found within the temple of Kerma. In China, bronze mirrors were manufactured from around 2000 BC, some of the earliest bronze and copper examples being produced by
7738-711: The Bulldog armoured personnel carrier . Light armoured units often utilise the Supacat "Jackal" MWMIK and Coyote tactical support vehicle for reconnaissance and fire support. The army has three main artillery systems: the M270 multiple launch rocket system (MLRS), the AS-90 and the L118 light gun . The MLRS, first used in Operation Granby , has an 85-kilometre (53 mi) standard range, or with
7884-401: The Caliphate mathematician Ibn Sahl in the tenth century. Mirrors can be classified in many ways; including by shape, support, reflective materials, manufacturing methods, and intended application. Typical mirror shapes are planar and curved mirrors. The surface of curved mirrors is often a part of a sphere . Mirrors that are meant to precisely concentrate parallel rays of light into
8030-418: The Eastern Association ), often commanded by local members of Parliament (both from the House of Commons and the House of Lords), while more than able to hold their own in the regions which Parliamentarians ('Roundheads") controlled, were unlikely to win the war. So Parliament initiated two actions. The Self-denying Ordinance forbade members of Parliament (with the notable exception of Oliver Cromwell , then
8176-477: The Far East , the British Army rallied against the Japanese in the Burma Campaign and regained the British Far Eastern colonial possessions. After the Second World War the British Army was significantly reduced in size, although National Service continued until 1960. This period saw decolonisation begin with the partition and independence of India and Pakistan, followed by the independence of British colonies in Africa and Asia. The Corps Warrant , which
8322-442: The Islamic State (ISIL). The British Army maintains a standing liability to support the civil authorities in certain circumstances, usually in either niche capabilities (e.g. explosive ordnance removal) or in general support of the civil authorities when their capacity is exceeded. In recent years this has been seen as army personnel supporting the civil authorities in the face of the 2001 United Kingdom foot-and-mouth outbreak ,
8468-445: The L17A2 under-barrel grenade launcher. In 2023, the Army Special Operations Brigade , which includes the Ranger Regiment , began using the L403A1 , an AR-pattern rifle also used by the Royal Marines . Some soldiers are equipped with the 7.62mm L129A1 sharpshooter rifle , which in 2018 formally replaced the L86A2 Light Support Weapon. Support fire is provided by the L7 general-purpose machine gun (GPMG), and indirect fire
8614-437: The Netherlands for the War of the Spanish Succession . Although all the regiments were now part of the new British military establishment, they remained under the old operational-command structure and retained much of the institutional ethos, customs and traditions of the standing armies created shortly after the Restoration of the Monarchy 47 years earlier. The order of seniority of the most-senior British Army line regiments
8760-424: The Ottoman Empire via Gallipoli , an unsuccessful attempt to capture Constantinople and secure a sea route to Russia . The First World War was the most devastating in British military history , with nearly 800,000 men killed and over two million wounded. Early in the war, the BEF was virtually destroyed and was replaced first by volunteers and then by a conscript force. Major battles included those at
8906-441: The PrSM , up to 500 km. The AS-90 is a 155 mm self-propelled armoured gun with a 24-kilometre (15 mi) range. The L118 light gun is a 105 mm towed gun, which is typically towed by a Pinzgauer all-terrain vehicle. To identify artillery targets, the army operates the TAIPAN artillery detection radar and utilises artillery sound ranging . For air defence it uses the new Sky Sabre system, which in 2021 replaced
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#17328553791909052-418: The Provisional Irish Republican Army (PIRA). Under the 1998 Good Friday Agreement , there was a gradual reduction in the number of soldiers deployed. In 2005, after the PIRA declared a ceasefire, the British Army dismantled posts, withdrew many troops and restored troop levels to those of a peacetime garrison. Operation Banner ended at midnight on 31 July 2007 after about 38 years of continuous deployment,
9198-488: The Qijia culture . Such metal mirrors remained the norm through to Greco-Roman Antiquity and throughout the Middle Ages in Europe . During the Roman Empire silver mirrors were in wide use by servants. Speculum metal is a highly reflective alloy of copper and tin that was used for mirrors until a couple of centuries ago. Such mirrors may have originated in China and India. Mirrors of speculum metal or any precious metal were hard to produce and were only owned by
9344-422: The Rapier . It also deploys the Very Short-Range Air Defence (VSHORAD) Starstreak HVM (high-velocity missile) launched by a single soldier or from a Stormer HVM vehicle-mounted launcher. Where armour is not required or mobility and speed are favoured the British Army utilises protected patrol vehicles, such as the Panther variant of the Iveco LMV , the Foxhound , and variants of the Cougar family (such as
9490-513: The Royal Navy 's Astute -class submarines instead use photonics masts , pioneered by the Royal Navy's HMS Trenchant , which lift an electronic imaging sensor-set above the water. Signals from the sensor-set travel electronically to workstations in the submarine's control center. While the cables carrying the signal must penetrate the submarine's hull, they use a much smaller and more easily sealed—and therefore less expensive and safer—hull opening than those required by periscopes. Eliminating
9636-533: The Schott Glass company, Walter Geffcken invented the first dielectric mirrors to use multilayer coatings. The Greek in Classical Antiquity were familiar with the use of mirrors to concentrate light. Parabolic mirrors were described and studied by the mathematician Diocles in his work On Burning Mirrors . Ptolemy conducted a number of experiments with curved polished iron mirrors, and discussed plane, convex spherical, and concave spherical mirrors in his Optics . Parabolic mirrors were also described by
9782-437: The Territorial Force as the army's volunteer reserve component, merging and reorganising the Volunteer Force, Militia and Yeomanry. Great Britain was challenged by other powers, primarily the German Empire and Nazi Germany , during the 20th century. A century earlier it vied with Napoleonic France for global pre-eminence, and Hanoverian Britain's natural allies were the kingdoms and principalities of northern Germany . By
9928-422: The United States Navy later invented a prismatic version for use in the American Civil War of 1861–1865. Submarines adopted periscopes early. Captain Arthur Krebs adapted two on the experimental French submarine Gymnote in 1888 and 1889. The Spanish inventor Isaac Peral equipped his submarine Peral (developed in 1886 but launched on September 8, 1888) with a fixed, non-retractable periscope that used
10074-438: The Vickers Tank Periscope MK.IV . The Gundlach-Vickers technology was shared with the American Army for use in its tanks including the Sherman , built to meet joint British and US requirements. This saw post-war controversy through legal action: "After the Second World War and a long court battle, in 1947 he, Rudolf Gundlach, received a large payment for his periscope patent from some of its producers." The USSR also copied
10220-506: The angle of incidence between n → {\displaystyle {\vec {n}}} and u → {\displaystyle {\vec {u}}} , but of opposite sign. This property can be explained by the physics of an electromagnetic plane wave that is incident to a flat surface that is electrically conductive or where the speed of light changes abruptly, as between two materials with different indices of refraction. More specifically,
10366-419: The 16th century, was to blow a cylinder of glass, cut off the ends, slice it along its length, and unroll it onto a flat hot plate. Venetian glassmakers also adopted lead glass for mirrors, because of its crystal-clarity and its easier workability. During the early European Renaissance , a fire-gilding technique developed to produce an even and highly reflective tin coating for glass mirrors. The back of
10512-501: The 1st century CE , with the development of soda-lime glass and glass blowing . The Roman scholar Pliny the Elder claims that artisans in Sidon (modern-day Lebanon ) were producing glass mirrors coated with lead or gold leaf in the back. The metal provided good reflectivity, and the glass provided a smooth surface and protected the metal from scratches and tarnishing. However, there
10658-688: The 2002 firefighters strike, widespread flooding in 2005, 2007, 2009, 2013 and 2014, Operation Temperer following the Manchester Arena bombing in 2017 and, most recently, Operation Rescript during the COVID-19 pandemic . Since 2016, the British Army has maintained a presence in the Baltic States in support of the NATO Enhanced Forward Presence strategy which responded to the 2014 Russian annexation of Crimea . The British Army leads
10804-829: The 2014 West African Ebola virus epidemic . In November 2001, as part of Operation Enduring Freedom with the United States, the United Kingdom deployed forces in Afghanistan to topple the Taliban in Operation Herrick . The 3rd Division were sent to Kabul to assist in the liberation of the capital and defeat Taliban forces in the mountains. In 2006 the British Army began concentrating on fighting Taliban forces and bringing security to Helmand Province , with about 9,500 British troops (including marines, airmen and sailors) deployed at its peak —the second-largest force after that of
10950-484: The American colonial rebels early in the war). Halifax, Nova Scotia and Bermuda were to become Imperial fortresses (although Bermuda, being safer from attack over water and impervious to attack overland, quickly became the most important in British North America), along with Malta and Gibraltar , providing bases in the eastern Atlantic Ocean and Mediterranean Sea for Royal Navy squadrons to control
11096-515: The British Army comprises 74,296 regular full-time personnel, 4,244 Gurkhas , 25,934 volunteer reserve personnel and 4,612 "other personnel", for a total of 109,086. The British Army traces back to 1707 and the formation of the united Kingdom of Great Britain which joined the Kingdoms of England and Scotland into a single state and, with that, united the English Army and the Scots Army as
11242-636: The British Army was deployed as a peacekeeping force from 1969 to 2007 in Operation Banner . Initially, this was (in the wake of unionist attacks on nationalist communities in Derry and Belfast ) to prevent further loyalist attacks on Catholic communities; it developed into support of the Royal Ulster Constabulary (RUC) and its successor, the Police Service of Northern Ireland (PSNI) against
11388-700: The British Army was one of two Regular Forces (there were also separate Reserve Forces ) within the British military (those parts of the British Armed Forces tasked with land warfare, as opposed to the naval forces), with the other having been the Ordnance Military Corps (made up of the Royal Artillery , Royal Engineers , and the Royal Sappers and Miners ) of the Board of Ordnance , which along with
11534-582: The British and the First French Empire of Napoleon Bonaparte stretched around the world; at its peak in 1813, the regular army contained over 250,000 men. A coalition of Anglo-Dutch and Prussian armies under the Duke of Wellington and Field Marshal von Blücher finally defeated Napoleon at Waterloo in 1815. The English were involved politically and militarily in Ireland. The campaign of English republican Protector Oliver Cromwell involved uncompromising treatment of
11680-439: The British military, mostly civilians. An estimated 100 soldiers committed suicide during Operation Banner or soon afterwards and a similar number died in accidents. A total of 6,116 were wounded. Sierra Leone The British Army deployed to Sierra Leone for Operation Palliser in 1999, under United Nations resolutions, to aid the government in quelling violent uprisings by militiamen. British troops also provided support during
11826-516: The Churchill and Cromwell, a similarly marked episcope provided a backup sighting mechanism aligned with a vane sight on the turret roof. Later, US-built Sherman tanks and British Centurion and Charioteer tanks replaced the main telescopic sight with a true periscopic sight in the primary role. The periscopic sight was linked to the gun itself, allowing elevation to be captured (rotation being fixed as part of rotating turret). The sights formed part of
11972-659: The Germans and Italians at the Second Battle of El Alamein in North Africa in 1942–1943 and helped drive them from Africa. It then fought through Italy and, with the help of American, Canadian, Australian, New Zealand, Indian and Free French forces, was the principal organiser and participant in the D-Day invasion of Normandy on 6 June 1944; nearly half the Allied soldiers were British. In
12118-601: The Irish towns (most notably Drogheda and Wexford ) which supported the Royalists during the English Civil War . The English Army (and the subsequent British Army) remained in Ireland primarily to suppress Irish revolts or disorder. In addition to its conflict with Irish nationalists, it was faced with the prospect of battling Anglo-Irish and Ulster Scots in Ireland who were angered by unfavourable taxation of Irish produce imported into Britain. With other Irish groups, they raised
12264-503: The Moon]. Hevelius saw military applications for his invention. Mikhail Lomonosov invented an "optical tube" which was similar to a periscope. In 1834, it was used in a submarine, designed by Karl Andreevich Schilder. In 1854, Hippolyte Marié-Davy invented the first naval periscope, consisting of a vertical tube with two small mirrors fixed at each end at 45°. Simon Lake used periscopes in his submarines in 1902. Sir Howard Grubb perfected
12410-823: The Ridgeback, Husky and Mastiff). For day-to-day utility work the army commonly uses the Land Rover Wolf , which is based on the Land Rover Defender . Specialist engineering vehicles include bomb-disposal robots such as the T7 Multi-Mission Robotic System and the modern variants of the Armoured Vehicle Royal Engineers , including the Titan bridge-layer, Trojan armoured engineer vehicle, Terrier armoured digger . Day-to-day utility work uses
12556-470: The Scots Greys was reassessed and based on their June 1685 entry into England. At that time there was only one English regiment of dragoons, and the Scots Greys eventually received the British Army rank of 2nd Dragoons. After 1700, British continental policy was to contain expansion by competing powers such as France and Spain. Although Spain was the dominant global power during the previous two centuries and
12702-694: The Somme and Passchendaele . Advances in technology saw the advent of the tank (and the creation of the Royal Tank Regiment ) and advances in aircraft design (and the creation of the Royal Flying Corps ) which would be decisive in future battles. Trench warfare dominated Western Front strategy for most of the war, and the use of chemical weapons (disabling and poison gases) added to the devastation. The Second World War broke out in September 1939 with
12848-716: The Soviet and German Army 's invasion of Poland . British assurances to the Poles led the British Empire to declare war on Germany . As in the First World War, a relatively small BEF was sent to France but then hastily evacuated from Dunkirk as the German forces swept through the Low Countries and across France in May 1940. After the British Army recovered from its earlier defeats, it defeated
12994-556: The Troubles . Following the 1994–1996 IRA ceasefires and since 1997, demilitarisation has been part of the peace process and the military presence has been reduced. On 25 June 2007 the 2nd Battalion of the Princess of Wales's Royal Regiment left the army complex in Bessbrook , County Armagh , ending the longest operation in British Army history. The British Army contributed 50,000 troops to
13140-579: The US. In December 2012 Prime Minister David Cameron announced that the combat mission would end in 2014, and troop numbers gradually fell as the Afghan National Army took over the brunt of the fighting. Between 2001 and 26 April 2014 a total of 453 British military personnel died in Afghan operations. Operation Herrick ended with the handover of Camp Bastion on 26 October 2014, but the British Army maintained
13286-752: The United States, in the American War of 1812 ), the British Army fought the Chinese in the First and Second Opium Wars and the Boxer Rebellion , Māori tribes in the first of the New Zealand Wars, Nawab Shiraj-ud-Daula's forces and British East India Company mutineers in the Sepoy Rebellion of 1857 , the Boers in the first and second Boer Wars, Irish Fenians in Canada during the Fenian raids and Irish separatists in
13432-599: The Wars of the Three Kingdoms, when a foreign expeditionary force was needed, such as the one that Henry V of England took to France and that fought at the Battle of Agincourt (1415), the army, a professional one, was raised for the duration of the expedition. During the Wars of the Three Kingdoms, the members of the English Long Parliament realised that the use of county militia organised into regional associations (such as
13578-559: The army saw the introduction of new weapons systems. Despite the decline of the British Empire, the army was engaged in Aden , Indonesia , Cyprus , Kenya and Malaya . In 1982, the British Army and the Royal Marines helped liberate the Falkland Islands during the conflict with Argentina after that country's invasion of the British territory. In the three decades following 1969,
13724-541: The army was heavily deployed in Northern Ireland 's Operation Banner to support the Royal Ulster Constabulary (later the Police Service of Northern Ireland ) in their conflict with republican paramilitary groups. The locally recruited Ulster Defence Regiment was formed, becoming home-service battalions of the Royal Irish Regiment in 1992 before it was disbanded in 2006. Over 700 soldiers were killed during
13870-412: The bulb's walls. This phenomenon was developed into the method of evaporation coating by Pohl and Pringsheim in 1912. John D. Strong used evaporation coating to make the first aluminium -coated telescope mirrors in the 1930s. The first dielectric mirror was created in 1937 by Auwarter using evaporated rhodium . The metal coating of glass mirrors is usually protected from abrasion and corrosion by
14016-642: The chief threat to England's early trans-Atlantic colonial ambitions, its influence was now waning. The territorial ambitions of the French, however, led to the War of the Spanish Succession and the later Napoleonic Wars . Although the Royal Navy is widely regarded as vital to the rise of the British Empire , the British Army played an important role in the formation of colonies, protectorates and dominions in
14162-416: The classical submarine periscope is very simple: two telescopes pointed into each other. If the two telescopes have different individual magnification, the difference between them causes an overall magnification or reduction. Johannes Hevelius described an early periscope (which he called a "polemoscope") with lenses in 1647 in his work Selenographia, sive Lunae descriptio [Selenography, or an account of
14308-745: The coalition which fought Iraq in the Persian Gulf War , and British forces controlled Kuwait after its liberation. Forty-seven British military personnel died during the war. The army was deployed to former Yugoslavia in 1992. Initially part of the United Nations Protection Force , in 1995 its command was transferred to the Implementation Force (IFOR) and then to the Stabilisation Force in Bosnia and Herzegovina (SFOR);
14454-531: The colours and the remainder in the Regular Reserve, remaining liable for recall to the colours if required. Among the other benefits, this thereby enabled the British Army to have a ready pool of recently trained men to draw upon in an emergency. The name of the Regular Reserve (which for a time was divided into a First Class and a Second Class ) has resulted in confusion with the Reserve Forces , which were
14600-462: The commitment rose to over 10,000 troops. In 1999, British forces under SFOR command were sent to Kosovo and the contingent increased to 19,000 troops. Between early 1993 and June 2010, 72 British military personnel died during operations in the former Yugoslavian countries of Bosnia, Kosovo and Macedonia. Although there have been permanent garrisons in Northern Ireland throughout its history,
14746-438: The completion of their first engagement. The size of the army also fluctuated greatly, increasing in war time, and drastically shrinking with peace. Battalions posted on garrison duty overseas were allowed an increase on their normal peacetime establishment, which resulted in their having surplus men on their return to a Home station. Consequently, soldiers engaging on short term enlistments were enabled to serve several years with
14892-621: The design and used it extensively in its tanks, including the T-34 and T-70 . The copies were based on Lend-Lease British vehicles, and many parts remain interchangeable. Germany also made and used copies. Periscopic sights were also introduced during the Second World War. In British use, the Vickers periscope was provided with sighting lines, enabling front and rear prisms to be directly aligned to gain an accurate direction. On later tanks such as
15038-518: The device in World War I. Morgan Robertson (1861–1915) claimed to have tried to patent the periscope: he described a submarine using a periscope in his fictional works. Periscopes, in some cases fixed to rifles , served in World War I (1914–1918) to enable soldiers to see over the tops of trenches , thus avoiding exposure to enemy fire (especially from snipers). The periscope rifle also saw use during
15184-399: The direction of the image in an equal yet opposite angle from which the light shines upon it. This allows the viewer to see themselves or objects behind them, or even objects that are at an angle from them but out of their field of view, such as around a corner. Natural mirrors have existed since prehistoric times, such as the surface of water, but people have been manufacturing mirrors out of
15330-496: The disbanded New Model Army , were formed between November 1660 and January 1661 and became a standing military force for England (financed by Parliament ). The Royal Scots and Irish Armies were financed by the parliaments of Scotland and Ireland . Parliamentary control was established by the Bill of Rights 1689 and Claim of Right Act 1689 , although the monarch continued to influence aspects of army administration until at least
15476-505: The end of the 19th century. After the Restoration, King Charles II pulled together four regiments of infantry and cavalry, calling them his guards, at a cost of £122,000 from his general budget. This became the foundation of the permanent English Army. By 1685, it had grown to number 7,500 soldiers in marching regiments, and 1,400 men permanently stationed in garrisons. A Monmouth Rebellion in 1685 allowed successor King James II to raise
15622-546: The extra prism. This design, patented by Rudolf Gundlach in 1936, first saw use in the Polish 7-TP light tank (produced from 1935 to 1939). As a part of Polish–British pre- World War II military cooperation, the patent was sold to Vickers-Armstrong where it saw further development for use in British tanks, including the Crusader , Churchill , Valentine , and Cromwell models as
15768-464: The forces to 20,000 men. There were 37,000 in 1678, when England played a role in the closing stage of the cross-channel Franco-Dutch War . After Protestant dual Monarchs William III , formerly William of the Dutch House of Orange , and his wife Mary II's joint accession to the throne after a short constitutional crisis with Parliament sending Mary's father, predecessor King James II, (who remained
15914-407: The glass was coated with a tin-mercury amalgam, and the mercury was then evaporated by heating the piece. This process caused less thermal shock to the glass than the older molten-lead method. The date and location of the discovery is unknown, but by the 16th century Venice was a center of mirror production using this technique. These Venetian mirrors were up to 40 inches (100 cm) square. For
16060-423: The greater availability of affordable mirrors. Mirrors are often produced by the wet deposition of silver, or sometimes nickel or chromium (the latter used most often in automotive mirrors) via electroplating directly onto the glass substrate. Glass mirrors for optical instruments are usually produced by vacuum deposition methods. These techniques can be traced to observations in the 1920s and 1930s that metal
16206-440: The incident rays are parallel among themselves but not parallel to the mirror's axis, or are divergent from a point that is not the focus – as when trying to form an image of an object that is near the mirror or spans a wide angle as seen from it. However, this aberration can be sufficiently small if the object image is sufficiently far from the mirror and spans a sufficiently small angle around its axis. Mirrors reflect an image to
16352-509: The later Restoration of the monarchy in 1660 with the accession of King Charles II . For many decades the alleged excesses of the New Model Army under the Protectorate / Commonwealth under Oliver Cromwell were used as propaganda (and still feature in Irish folklore) and the Whig Party element recoiled from allowing a standing army to continue with the agreed-upon rights and privileges under
16498-488: The longest in British Army history. According to an internal document released in 2007, the British Army had failed to defeat the IRA but made it impossible for them to win by violence. Operation Helvetic replaced Operation Banner in 2007, maintaining fewer service personnel in a more-benign environment. Of the 300,000 troops who served in Northern Ireland since 1969, there were 763 British military personnel killed and 306 killed by
16644-526: The middle of the 19th century, Britain and France were allies in preventing Russia's appropriation of the Ottoman Empire , although the fear of French invasion led shortly afterwards to the creation of the Volunteer Force. By the first decade of the 20th century, the United Kingdom was allied with France (by the Entente Cordiale ) and Russia (which had a secret agreement with France for mutual support in
16790-399: The mirror (incident light). This property, called specular reflection , distinguishes a mirror from objects that diffuse light, breaking up the wave and scattering it in many directions (such as flat-white paint). Thus, a mirror can be any surface in which the texture or roughness of the surface is smaller (smoother) than the wavelength of the waves. When looking at a mirror, one will see
16936-672: The mirror always appear closer in the virtual image, and objects farther from the surface always appear symmetrically farther away regardless of angle. British Army The British Army is the principal land warfare force of the United Kingdom , British Overseas Territories and Crown Dependencies , a part of the British Armed Forces along with the Naval Service and the Royal Air Force . As of 1 July 2024,
17082-440: The new English army to 74,000, and then a few years later to 94,000 in 1694. Parliament was very nervous and reduced the cadre to 70,000 in 1697. Scotland and Ireland had theoretically separate military establishments, but they were unofficially merged with the English Crown force. By the time of the 1707 Acts of Union , many regiments of the English and Scottish armies were combined under one operational command and stationed in
17228-444: The normal vector n → {\displaystyle {\vec {n}}} , and direction vector v → {\displaystyle {\vec {v}}} of the reflected beam will be coplanar , and the angle between n → {\displaystyle {\vec {n}}} and v → {\displaystyle {\vec {v}}} will be equal to
17374-447: The observer. However, unlike a projected image on a screen, an image does not actually exist on the surface of the mirror. For example, when two people look at each other in a mirror, both see different images on the same surface. When the light waves converge through the lens of the eye they interfere with each other to form the image on the surface of the retina , and since both viewers see waves coming from different directions, each sees
17520-458: The oceans and trade routes, and heavily garrisoned by the British Army both for defence of the bases and to provide mobile military forces to work with the Navy in amphibious operations throughout their regions. The British Army was heavily involved in the Napoleonic Wars , participating in a number of campaigns in Europe (including continuous deployment in the Peninsular War ), the Caribbean , North Africa and North America . The war between
17666-417: The originally civilian Commissariat Department , stores and supply departments, as well as barracks and other departments, were absorbed into the British Army when the Board of Ordnance was abolished in 1855. Various other civilian departments of the board were absorbed into the War Office . The British Army has seen action in major wars between the world's great powers , including the Seven Years' War ,
17812-457: The other focus. A convex parabolic mirror, on the other hand, will reflect rays that are parallel to its axis into rays that seem to emanate from the focus of the surface, behind the mirror. Conversely, it will reflect incoming rays that converge toward that point into rays that are parallel to the axis. A convex mirror that is part of a prolate ellipsoid will reflect rays that converge towards one focus into divergent rays that seem to emanate from
17958-531: The other focus. Spherical mirrors do not reflect parallel rays to rays that converge to or diverge from a single point, or vice versa, due to spherical aberration . However, a spherical mirror whose diameter is sufficiently small compared to the sphere's radius will behave very similarly to a parabolic mirror whose axis goes through the mirror's center and the center of that sphere; so that spherical mirrors can substitute for parabolic ones in many applications. A similar aberration occurs with parabolic mirrors when
18104-401: The over wing exit row to regulate the landing gear. High speed and hypersonic aircraft such as the North American X-15 used a periscope. Mirror A mirror , also known as a looking glass , is an object that reflects an image . Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse
18250-521: The overall periscope, providing the gunner with greater overall vision than previously possible with the telescopic sight. The FV4201 Chieftain used the TESS (TElescopic Sighting System) developed in the early 1980s that was later sold as surplus for use on the RAF Phantom aircraft. In modern use, specialised periscopes can also provide night vision. The Embedded Image Periscope (EIP) designed and patented by Kent Periscopes provides standard unity vision periscope functionality for normal daytime viewing of
18396-436: The parallel Seven Years' War and suppressed a Native / Indian North Americans uprising in Pontiac's War around the Great Lakes . The British Army was defeated in the American Revolutionary War , losing the Thirteen Colonies but retaining The Canadas and The Maritimes as in British North America , including Bermuda (originally part of the Colony of Virginia , and which had been originally strongly sympathetic to
18542-649: The poor quality, high cost, and small size of glass mirrors, solid-metal mirrors (primarily of steel) remained in common use until the late nineteenth century. Silver-coated metal mirrors were developed in China as early as 500 CE. The bare metal was coated with an amalgam , then heated until the mercury boiled away. The evolution of glass mirrors in the Middle Ages followed improvements in glassmaking technology. Glassmakers in France made flat glass plates by blowing glass bubbles, spinning them rapidly to flatten them, and cutting rectangles out of them. A better method, developed in Germany and perfected in Venice by
18688-481: The pre-existing part-time, local-service home-defence forces that were auxiliary to the British Army (or Regular Force ), but not originally part of it: the Yeomanry , Militia (or Constitutional Force ) and Volunteer Force . These were consequently also referred to as Auxiliary Forces or Local Forces . The late-19th-century Cardwell and Childers Reforms gave the army its modern shape and redefined its regimental system . The 1907 Haldane Reforms created
18834-411: The protectoscope allows the vision slit to be blanked off with spaced armoured plate. This prevents a potential ingress point for small arms fire, with only a small difference in vision height, but still requires the armour to be cut. In the context of armoured fighting vehicles , such as tanks , a periscopic vision device may also be referred to as an episcope . In this context a periscope refers to
18980-410: The rank of English, Irish and Scots regiments serving in the Netherlands; the regiment which became known as the Scots Greys were designated the 4th Dragoons because there were three English regiments raised prior to 1688 when the Scots Greys were first placed in the English establishment. In 1713, when a new board of general officers was convened to decide the rank of several regiments, the seniority of
19126-436: The reflecting surface, are much more rugged than mirrors. They may have additional optical capabilities such as range-finding and targeting. The mechanical systems of submarine periscopes typically use hydraulics and need to be quite sturdy to withstand the drag through water. The periscope chassis may also support a radio or radar antenna. Submarines traditionally had two periscopes; a navigation or observation periscope and
19272-407: The reflective layer is usually some metal like silver, tin, nickel , or chromium , deposited by a wet process; or aluminium, deposited by sputtering or evaporation in vacuum. The reflective layer may also be made of one or more layers of transparent materials with suitable indices of refraction . The structural material may be a metal, in which case the reflecting layer may be just the surface of
19418-491: The return of a king. The militia acts of 1661 and 1662 prevented local authorities from calling up militia and oppressing their own local opponents. Calling up the militia was possible only if the king and local elites agreed to do so. King Charles II and his " Cavalier " / Royalist supporters favoured a new army under royal control, and immediately after the Restoration of 1660 to 1661 began working on its establishment. The first English Army regiments, including elements of
19564-465: The same degree of curvature and vergence , in an equal yet opposite direction, as the original waves. This allows the waves to form an image when they are focused through a lens, just as if the waves had originated from the direction of the mirror. The light can also be pictured as rays (imaginary lines radiating from the light source, that are always perpendicular to the waves). These rays are reflected at an equal yet opposite angle from which they strike
19710-588: The same. Metal concave dishes are often used to reflect infrared light (such as in space heaters ) or microwaves (as in satellite TV antennas). Liquid metal telescopes use a surface of liquid metal such as mercury. Mirrors that reflect only part of the light, while transmitting some of the rest, can be made with very thin metal layers or suitable combinations of dielectric layers. They are typically used as beamsplitters . A dichroic mirror , in particular, has surface that reflects certain wavelengths of light, while letting other wavelengths pass through. A cold mirror
19856-414: The surface of the water and in the air. When not in use, a submarine's periscope retracts into the hull . A submarine commander in tactical conditions must exercise discretion when using his periscope, since it creates a visible wake (and may also become detectable by radar ), giving away the submarine's position. Marie-Davey built a simple, fixed naval periscope using mirrors in 1854. Thomas H. Doughty of
20002-419: The telescoping tube running through the conning tower also allows greater freedom in designing the pressure hull and in placing internal equipment. Periscopes have also been used on aircraft for sections with limited view. The first known use of aircraft periscope was on the Spirit of St. Louis . The Vickers VC10 had a periscope that could be used on four locations of the aircraft fuselage, V-Bombers such as
20148-447: The vehicle roof. Prior to periscopes, direct vision slits were cut in the armour for occupants to see out. Periscopes permit view outside of the vehicle without needing to cut these weaker vision openings in the front and side armour, better protecting the vehicle and occupants. A protectoscope is a related periscopic vision device designed to provide a window in armoured plate, similar to a direct vision slit. A compact periscope inside
20294-407: The vehicle surroundings plus the ability to display digital images from a range of on-vehicle sensors and cameras (including thermal and low light) such that the resulting image appears "embedded" internally within the unit and projected at a comfortable viewing positions. Periscopes allow a submarine , when submerged at a relatively shallow depth, to search visually for nearby targets and threats on
20440-575: The war – this was an infantry rifle sighted by means of a periscope, so the shooter could aim and fire the weapon from a safe position below the trench parapet. During World War II (1939–1945), artillery observers and officers used specifically manufactured periscope binoculars with different mountings. Some of them also allowed estimating the distance to a target, as they were designed as stereoscopic rangefinders . Tanks and armoured vehicles use periscopes: they enable drivers, tank commanders, and other vehicle occupants to inspect their situation through
20586-599: The wealthy. Common metal mirrors tarnished and required frequent polishing. Bronze mirrors had low reflectivity and poor color rendering , and stone mirrors were much worse in this regard. These defects explain the New Testament reference in 1 Corinthians 13 to seeing "as in a mirror, darkly." The Greek philosopher Socrates urged young people to look at themselves in mirrors so that, if they were beautiful, they would become worthy of their beauty, and if they were ugly, they would know how to hide their disgrace through learning. Glass began to be used for mirrors in
20732-611: The withdrawal of civilians, all British troops had left by the end of August 2021. In 2003, the United Kingdom was a major contributor to the invasion of Iraq , sending a force of over 46,000 military personnel. The British Army controlled southern Iraq, and maintained a peace-keeping presence in Basra . All British troops were withdrawn from Iraq by 30 April 2009, after the Iraqi government refused to extend their mandate. One hundred and seventy-nine British military personnel died in Iraqi operations. The British Armed Forces returned to Iraq in 2014 as part of Operation Shader to counter
20878-432: Was an important manufacturer, and Bohemian and German glass, often rather cheaper, was also important. The invention of the silvered-glass mirror is credited to German chemist Justus von Liebig in 1835. His wet deposition process involved the deposition of a thin layer of metallic silver onto glass through the chemical reduction of silver nitrate . This silvering process was adapted for mass manufacturing and led to
21024-425: Was being ejected from electrodes in gas discharge lamps and condensed on the glass walls forming a mirror-like coating. The phenomenon, called sputtering , was developed into an industrial metal-coating method with the development of semiconductor technology in the 1970s. A similar phenomenon had been observed with incandescent light bulbs : the metal in the hot filament would slowly sublimate and condense on
21170-420: Was declared in 1951. Although the British Army was a major participant in Korea in the early 1950s and Suez in 1956, during this period Britain's role in world events was reduced and the army was downsized. The British Army of the Rhine , consisting of I (BR) Corps , remained in Germany as a bulwark against Soviet invasion. The Cold War continued, with significant technological advances in warfare, and
21316-411: Was leaked through industrial espionage. French workshops succeeded in large-scale industrialization of the process, eventually making mirrors affordable to the masses, in spite of the toxicity of mercury's vapor. The invention of the ribbon machine in the late Industrial Revolution allowed modern glass panes to be produced in bulk. The Saint-Gobain factory, founded by royal initiative in France,
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