Fundamental Properties - GRE Subject Test: Physics
Card 0 of 2
A particle traveling through glass (index of refraction 1.33) emits Cherenkov radiation. Which of the following is a possible speed of the particle?
A particle traveling through glass (index of refraction 1.33) emits Cherenkov radiation. Which of the following is a possible speed of the particle?
Cherenkov radiation is emitted by a particle traveling faster than the phase velocity of light in that medium. Because 
, the phase velocity of light in the glass is:
This is the minimum velocity of a particle to be emitting Cherenkov radiation in glass. This eliminates all answers except 
and 
. The latter is impossible because it is greater than the speed of light in a vacuum, therefore the answer is .
Cherenkov radiation is emitted by a particle traveling faster than the phase velocity of light in that medium. Because
This is the minimum velocity of a particle to be emitting Cherenkov radiation in glass. This eliminates all answers except
Compare your answer with the correct one above
A monochromatic beam of 
light travels through a material with a phase velocity of 
. What is the refractive index of the material?
A monochromatic beam of
The phase velocity of light through a medium with refractive index 
is given by:
Solving this for 
and substituting our given value of 
:
The phase velocity of light through a medium with refractive index
Solving this for
Compare your answer with the correct one above