GRE Subject Test: Physics : Waves
Study concepts, example questions & explanations for GRE Subject Test: Physics
All GRE Subject Test: Physics Resources
Example Questions
Example Question #1 : Waves
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 
This is the minimum velocity of a particle to be emitting Cherenkov radiation in glass. This eliminates all answers except 
Example Question #2 : Waves
A monochromatic beam of 
The phase velocity of light through a medium with refractive index 
Solving this for 
Example Question #3 : Waves
A double slit experiment is set up with the following parameters: two slits are a separated by a distance 
The condition for constructive interference with double slit diffraction is given by:
Where 
Solving for the angle and using the small angle approximation, we get;
The distance 
Again, with the help of the small angle approximation. Setting the two thetas equal to each other and solving for 
For the central band, 
Example Question #4 : Waves
Two waves with frequencies: 
The beat from two combined sound waves is:
Example Question #5 : Waves
A beam of light, with wavelength 
The equation describing maxima of a diffraction grating is:
Where d is the separation of slits, which can also be expressed as:
Substituting d into the first equation and making the small angle approximation, one can solve for 
Note that the angle had to be converted from degrees to radians. Finally, the question asks for lines per centimeter, not meter, so the answer becomes 
Example Question #6 : Waves
A car's horn has a frequency of 
The equation for the Doppler effect with frequency for a moving source is given by:
Where 
All GRE Subject Test: Physics Resources
