Inverse Doppler effect
Encyclopedia
While the usual Doppler effect
means that the frequency
increases if the observer approaches the source – and decreases as they move away from each other – the theorists have speculated, since 1943, about the possibility that these rules may be interchanged. That would create an inverse Doppler effect.
An experiment that claimed to have detected this effect was conducted by Nigel Seddon and Trevor Bearpark in Bristol
, United Kingdom
in 2003.
Researchers form Swinburne University of Technology
and the University of Shanghai for Science and Technology
showed that this effect can be observed in Optical frequencies as well. This was made possible by growing a photonic crystal
and projecting a laser beam into the crystal. This will make the crystal act like a super prism
and the inverse Doppler effect can be observed.
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
means that the frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
increases if the observer approaches the source – and decreases as they move away from each other – the theorists have speculated, since 1943, about the possibility that these rules may be interchanged. That would create an inverse Doppler effect.
An experiment that claimed to have detected this effect was conducted by Nigel Seddon and Trevor Bearpark in Bristol
Bristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
in 2003.
Researchers form Swinburne University of Technology
Swinburne University of Technology
Swinburne University of Technology is an Australian public dual sector university based in Melbourne, Victoria. The institution was founded by the Honourable George Swinburne in 1908 and achieved university status in June 1992...
and the University of Shanghai for Science and Technology
University of Shanghai for Science and Technology
University of Shanghai for Science and Technology founded in 1906, is a public university in Shanghai, People's Republic of China...
showed that this effect can be observed in Optical frequencies as well. This was made possible by growing a photonic crystal
Photonic crystal
Photonic crystals are periodic optical nanostructures that are designed to affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons...
and projecting a laser beam into the crystal. This will make the crystal act like a super prism
Superprism
A superprism is a photonic crystal in which an entering beam of light will lead to an extremely large angular dispersion. The ability of the photonic crystal to send optical beams with different wavelengths to considerably different angles in space in superprisms has been used to demonstrate...
and the inverse Doppler effect can be observed.