Electromagnetic radiation is emitted when a charged particle movesthrough a medium faster than the local speed of light. Thisradiation is known as Cerenkov radiation. Cerenkov radiation isfound in many interesting places such as particle detectors andnuclear reactors and can even be seen by astronauts when cosmicrays traverse their eyes. It should be stressed that the particleis never going faster than the speed of light in vacuum (or c),just faster than the speed of light in the material (which isalways less than c). The creation of Cerenkov radiation occurs inmuch the same way that a sonic boom is created when a plane ismoving faster than the speed of sound in the air. The variouswavefronts that propagate in the material add coherently to createan effective shock wave. In this problem, you will become familiarwith this type of radiation and learn how to use its properties toget information about the particles that created it.
A)What is the threshold velocity v_threshold (water) (i.e., theminimum velocity) for creating Cerenkov light from a chargedparticle as it travels through water (which has an index ofrefraction of n=1.33)?
v_threshold (water) =c
B)What is the threshold velocity v_threshold (ethanol) for creatingCerenkov light from a charged particle as it travels throughethanol (which has an index of refraction of n=1.36)?
v_threshold (ethanol) =c
C)Which of the following best explains why neutrally chargedparticles can't give off Cerenkov radiation?
a)Neutral particles are too heavy to emit radiation.
b)Neutral particles don't interact with the electromagnetic fieldsof the medium.
c)Neutral particles can't move above the threshold velocity forCerenkov radiation.
d)Charged particles hit the nuclei of the material more often andthus create more radiation