date_of_birth ernst lecher
World War II ( often abbreviated to WWII or WW2 ), also known as the Second World War , was a global war that lasted from ___MASK14___ to ___MASK40___ , although related conflicts began earlier . It involved the vast majority of the world ' s nations  including all of the great powers  eventually forming two opposing military alliances : the Allies and the Axis . It was the most widespread war in history , and directly involved more than 100 million people from over 30 countries . In a state of " total war ", the major participants threw their entire economic , industrial , and scientific capabilities behind the war effort , erasing the distinction between civilian and military resources . Marked by mass deaths of civilians , including the Holocaust ( in which approximately 11 million people were killed ) and the strategic bombing of industrial and population centres ( in which approximately one million were killed , and which included the atomic bombings of Hiroshima and Nagasaki ), it resulted in an estimated 50 million to 85 million fatalities . These made World War II the deadliest conflict in human history . Lambda ( uppercase ', lowercase '; " lam ( b ) da ") is the 11th letter of the Greek alphabet . In the system of Greek numerals lambda has a value of ___MASK74___ . Lambda is related to the Phoenician letter Lamed . Letters in other alphabets that stemmed from lambda include the Latin L and the Cyrillic letter El (  ,  ). The ancient grammarians and dramatists give evidence to the pronunciation as in Classical Greek times . In Modern Greek the name of the letter ,  , is pronounced ; the spoken letter itself has the sound of "" as with Latinate " L ". The United States Navy ( USN ) is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States . The U . S . Navy is the largest , most capable navy in the world , with the highest combined battle fleet tonnage . The U . S . Navy has the world ' s largest aircraft carrier fleet , with ten in service , two in the reserve fleet , and three new carriers under construction . The service has 323 , ___MASK2___ personnel on active duty and 108 , 515 in the Navy Reserve . It has ___MASK30___ deployable combat vessels and more than ___MASK6___ , 700 aircraft in active service . World War I ( WWI or WW1 ), also known as the First World War , or the Great War , was a global war originating in Europe that lasted from ___MASK38___ July ___MASK67___ to 11 ___MASK77___ . More than 70 million military personnel , including 60 million Europeans , were mobilised in one of the largest wars in history . Over nine million combatants and seven million civilians died as a result of the war ( including the victims of a number of genocides ), a casualty rate exacerbated by the belligerents ' technological and industrial sophistication , and the tactical stalemate caused by gruelling trench warfare . It was one of the deadliest conflicts in history , and paved the way for major political changes , including revolutions in many of the nations involved . Slovakia , officially the Slovak Republic , is a landlocked country in Central Europe . It is bordered by the Czech Republic and Austria to the west , Poland to the north , Ukraine to the east and Hungary to the south . Slovakia ' s territory spans about and is mostly mountainous . The population is over ___MASK86___ million and comprises mostly ethnic Slovaks . The capital and largest city is Bratislava . The official language is Slovak , a member of the Slavic language family . In physics , sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement , through a transmission medium such as air or water . In physiology and psychology , sound is the " reception " of such waves and their " perception " by the brain . Humans can hear sound waves with frequencies between about ___MASK11___ Hz and ___MASK11___ kHz . Sound above ___MASK11___ kHz is ultrasound and below ___MASK11___ Hz is infrasound . Other animals have different hearing ranges . Ernst Lecher ( ___MASK8___  ___MASK93___ July ___MASK91___ ) was an Austrian physicist who , from ___MASK99___ , was head of the " First Institute of Physics " in Vienna . He is remembered for developing an apparatus  " Lecher lines " to measure the wavelength and frequency of electromagnetic waves . He gave his name to the Ernst - Lecher - Institut , a radar research establishment set up in the 1940s in Reichenau , south of Vienna , which is now a part of the German research institute Max Planck Institute . Heinrich Rudolf Hertz ( ___MASK87___  ___MASK33___ January 1894 ) was a German physicist who first conclusively proved the existence of the electromagnetic waves theorized by James Clerk Maxwell ' s electromagnetic theory of light . Hertz proved the theory by engineering instruments to transmit and receive radio pulses using experimental procedures that ruled out all other known wireless phenomena . The unit of frequency  cycle per second  was named the " hertz " in his honor . Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum . The word usually refers to visible light , which is visible to the human eye and is responsible for the sense of sight . Visible light is usually defined as having wavelengths in the range of ___MASK19___  700 nanometres ( nm ), or ___MASK59___ . 00 × 10 to 7 . 00 × 10 m , between the infrared ( with longer wavelengths ) and the ultraviolet ( with shorter wavelengths ). This wavelength means a frequency range of roughly 430  750 terahertz ( THz ). Radar is an object - detection system that uses radio waves to determine the range , angle , or velocity of objects . It can be used to detect aircraft , ships , spacecraft , guided missiles , motor vehicles , weather formations , and terrain . A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain , a transmitting antenna , a receiving antenna ( often the same antenna is used for transmitting and receiving ) and a receiver and processor to determine properties of the object ( s ). Radio waves ( pulsed or continuous ) from the transmitter reflect off the object and return to the receiver , giving information about the object ' s location and speed . Radar was developed secretly for military use by several nations in the period before and during World War II . The term " RADAR " was coined in ___MASK3___ by the United States Navy as an acronym for RAdio Detection And Ranging or RAdio Direction And Ranging . The term " radar " has since entered English and other languages as a common noun , losing all capitalization . Frequency is the number of occurrences of a repeating event per unit time . It is also referred to as temporal frequency , which emphasizes the contrast to spatial frequency and angular frequency . The period is the duration of time of one cycle in a repeating event , so the period is the reciprocal of the frequency . For example , if a newborn baby ' s heart beats at a frequency of ___MASK47___ times a minute , its period  the time interval between beats  is half a second ( that is , 60 seconds divided by ___MASK47___ beats ). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena , such as mechanical vibrations , audio ( sound ) signals , radio waves , and light . Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter ; with frequencies between and . This broad definition includes both UHF and EHF ( millimeter wave ) bands , and various sources use different boundaries . In all cases , microwaves include the entire SHF band ( ___MASK6___ to 30 GHz , or ___MASK98___ to ___MASK33___ cm ) at minimum , with RF engineering often restricting the range between ___MASK33___ and 100 GHz ( 300 and ___MASK6___ mm ). Frequencies in the microwave range are often referred to by their IEEE radar band designations : S , C , X , K , K , or K band , or by similar NATO or EU designations . Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light . Radio waves have frequencies as high as ___MASK92___ GHz to as low as ___MASK6___ kHz , though some definitions describe waves above ___MASK33___ or ___MASK6___ GHz as microwaves , or include waves of any lower frequency . At ___MASK92___ GHz , the corresponding wavelength is , and at ___MASK6___ kHz is . Like all other electromagnetic waves , they travel at the speed of light . Naturally occurring radio waves are generated by lightning , or by astronomical objects . The European Union ( EU ) is a political and economic union of member states that are located primarily in Europe . It has an area of , and an estimated population of over ___MASK75___ million . The EU has developed an internal single market through a standardised system of laws that apply in all member states . EU policies aim to ensure the free movement of people , goods , services , and capital within the internal market , enact legislation in justice and home affairs , and maintain common policies on trade , agriculture , fisheries , and regional development . Within the Schengen Area , passport controls have been abolished . A monetary union was established in ___MASK50___ and came into full force in 2002 , and is composed of 19 EU member states which use the euro currency . A television set , more commonly called a television , TV , TV set , television receiver , or telly , is a device that combines a tuner , display , and loudspeakers for the purpose of viewing television . Introduced in the late 1920s in mechanical form , television sets became a popular consumer product after World War II in electronic form , using cathode ray tubes . The addition of color to broadcast television after ___MASK7___ further increased the popularity of television sets in the 1960s , and an outdoor antenna became a common feature of suburban homes . The ubiquitous television set became the display device for the first recorded media in the 1970s , such as Betamax , VHS and later DVD . It was also the display device for the first generation of home computers ( e . g ., Timex Sinclair 1000 ) and video game consoles ( e . g ., Atari ) in the 1980s . In the 2010s flat panel television incorporating liquid - crystal displays , especially LED - backlit LCDs , largely replaced cathode ray tubes and other displays . Vienna is the capital and largest city of Austria and one of the nine states of Austria . Vienna is Austria ' s primary city , with a population of about ___MASK33___ . 8 million ( 2 . ___MASK61___ million within the metropolitan area , nearly one third of Austria ' s population ), and its cultural , economic , and political centre . It is the 7th - largest city by population within city limits in the European Union . Until the beginning of the 20th century , it was the largest German - speaking city in the world , and before the splitting of the Austro - Hungarian Empire in World War I , the city had 2 million inhabitants . Today , it has the second largest number of German speakers after Berlin . Vienna is host to many major international organizations , including the United Nations and OPEC . The city is located in the eastern part of Austria and is close to the borders of the Czech Republic , Slovakia , and Hungary . These regions work together in a European Centrope border region . Along with nearby Bratislava , Vienna forms a metropolitan region with 3 million inhabitants . In 2001 , the city centre was designated a UNESCO World Heritage Site . The United Nations ( UN ) is an intergovernmental organization to promote international co - operation . A replacement for the ineffective League of Nations , the organization was established on 24 October ___MASK40___ after World War II in order to prevent another such conflict . At its founding , the UN had 51 member states ; there are now 193 . The headquarters of the United Nations is in Manhattan , New York City , and experiences extraterritoriality . Further main offices are situated in Geneva , Nairobi , and Vienna . The organization is financed by assessed and voluntary contributions from its member states . Its objectives include maintaining international peace and security , promoting human rights , fostering social and economic development , protecting the environment , and providing humanitarian aid in cases of famine , natural disaster , and armed conflict . International Organization is a quarterly peer - reviewed academic journal that covers the entire field of international affairs . It was established in ___MASK44___ and is published by Cambridge University Press on behalf of the International Organization Foundation . The editor - in - chief is Jon Pevehouse ( University of Wisconsin  Madison ). Berlin is the capital and the largest city of Germany as well as one of its constituent 16 states . With a population of approximately ___MASK6___ . 5 million people , Berlin is the second most populous city proper and the seventh most populous urban area in the European Union . Located in northeastern Germany on the banks of rivers Spree and Havel , it is the centre of the Berlin - Brandenburg Metropolitan Region , which has about ___MASK61___ million residents from more than 180 nations . Due to its location in the European Plain , Berlin is influenced by a temperate seasonal climate . Around one - third of the city ' s area is composed of forests , parks , gardens , rivers and lakes . In electronics , a Lecher line or Lecher wires is a pair of parallel wires or rods that were used to measure the wavelength of radio waves , mainly at UHF and microwave frequencies . They form a short length of balanced transmission line ( a resonant stub ). When attached to a source of radio - frequency power such as a radio transmitter , the radio waves form standing waves along their length . By sliding a conductive bar that bridges the two wires along their length , the length of the waves can be physically measured . Austrian physicist Ernst Lecher , improving on techniques used by Oliver Lodge and Heinrich Hertz , developed this method of measuring wavelength around ___MASK62___ . Lecher lines were used as frequency measuring devices until frequency counters became available after World War 2 . They were also used as components , often called " resonant stubs ", in UHF and microwave radio equipment such as transmitters , radar sets , and television sets , serving as tank circuits , filters , and impedance - matching devices . They are used at frequencies between HF / VHF , where lumped components are used , and UHF / SHF , where resonant cavities are more practical . Sir Oliver Joseph Lodge , ( ___MASK25___  ___MASK66___ August ___MASK3___ ) was a British physicist and writer involved in the development of , and holder of key patents for , radio . He identified electromagnetic radiation independent of Hertz ' proof and at his 1894 Royal Institution lectures ("" The Work of Hertz and Some of His Successors ""), Lodge demonstrated an early radio wave detector he named the " coherer ". In 1898 he was awarded the " syntonic " ( or tuning ) patent by the United States Patent Office . Lodge was Principal of the University of Birmingham from 1900 to 1920 . The second ( symbol : s ) ( abbreviated s or sec ) is the base unit of time in the International System of Units ( SI ). It is qualitatively defined as the " second " division of the hour by sixty , the first division by sixty being the minute . SI definition of second is " the duration of 9 ___MASK72___ 631 ___MASK68___ periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom ". Seconds may be measured using a mechanical , electrical or an atomic clock . The Czech Republic , also known by the short name Czechia , is a nation state in Central Europe bordered by Germany to the west , Austria to the south , Slovakia to the east and Poland to the northeast . The Czech Republic covers an area of with mostly temperate continental climate and oceanic climate . It is a unitary parliamentary republic , has ___MASK98___ . 5 million inhabitants and the capital and largest city is Prague , with over ___MASK33___ . 2 million residents . The Czech Republic includes the historical territories of Bohemia , Moravia , and Czech Silesia . In physics , the wavelength of a sinusoidal wave is the spatial period of the wave  the distance over which the wave ' s shape repeats , and thus the inverse of the spatial frequency . It is usually determined by considering the distance between consecutive corresponding points of the same phase , such as crests , troughs , or zero crossings and is a characteristic of both traveling waves and standing waves , as well as other spatial wave patterns . Wavelength is commonly designated by the Greek letter " lambda " (  ). The concept can also be applied to periodic waves of non - sinusoidal shape . The term " wavelength " is also sometimes applied to modulated waves , and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids . Organization of the Petroleum Exporting Countries ( OPEC , , or OPEP in several other languages ) is an intergovernmental organization of 13 nations , founded in ___MASK24___ in Baghdad by the first five members ( Iran , Iraq , Kuwait , Saudi Arabia , Venezuela ), and headquartered since 1965 in Vienna . As of 2015 , the 13 countries accounted for an estimated 42 percent of global oil production and 73 percent of the world ' s " proven " oil reserves , giving OPEC a major influence on global oil prices that were previously determined by American - dominated multinational oil companies . Hungary is a unitary parliamentary republic in Central Europe . It covers an area of , situated in the Carpathian Basin and bordered by Slovakia to the north , Romania to the east , Serbia to the south , Croatia to the southwest , Slovenia to the west , Austria to the northwest , and Ukraine to the northeast . With about ___MASK98___ million inhabitants , Hungary is a medium - sized member state of the European Union . The official language is Hungarian , which is the most widely spoken Uralic language in the world . Hungary ' s capital and largest metropolis is Budapest , a significant economic hub , classified as an Alpha - global city . Major urban areas include Debrecen , Szeged , Miskolc , Pécs and Gyr . Ernst Lecher ( ___MASK55___ -- 1926 ) was an Austrian physicist who , from 1909 , was head of the First Institute of Physics in Vienna . He is remembered for developing an apparatus -- `` Lecher lines '' -- to measure the wavelength and frequency of electromagnetic waves . He gave his name to the Ernst - Lecher - Institut , a radar research establishment set up in the 1940s in Reichenau , south of Vienna , which is now a part of the German research institute Max Planck Institute . Lecher ' s father , Zacharias K Lecher , was editor of Vienna ' s leading daily newspaper , Die Presse , and helped to publicise the discovery of X - rays of his German colleague Wilhelm Röntgen in 1896 . Lecher ' s nephew , Konrad Zacharias Lorenz , won the Nobel Prize in Physiology or Medicine in 1973 . Bratislava ( or also known by ) is the capital of Slovakia , and with a population of about ___MASK21___ , 000 , the country ' s largest city . The greater metropolitan area is home to more than ___MASK79___ , 000 people . Bratislava is in southwestern Slovakia , occupying both banks of the River Danube and the left bank of the River Morava . Bordering Austria and Hungary , it is the only national capital that borders two sovereign states .