A Michelson interferometer is set up for microwaves. Initially the reflectors are placed so the detector reads a maximum. When one of the reflectors is moved 12 cm, the reading goes from a maximum to a minimum and back to maximum six times. What is the wavelength of the microwaves?
A) 0.5 cm
B) 4 cm
C) 1 cm
D) 2 cm

Question

Quizplus · Accepted Answer

In a Michelson interferometer, when one of the mirrors is moved, the path difference between the two arms of the interferometer changes. 
At a maximum reading, the two waves from the two mirrors are in phase with each other, and at a minimum reading, the two waves are out of phase with each other and cancel out.
If moving one of the mirrors by 12 cm causes the pattern to repeat six times, then the total path difference between the two arms is equal to six times the wavelength of the microwaves.
Therefore, 12 cm = 6λ
Solving for λ, we get λ = 2 cm.

Therefore, the best choice is B) 4 cm, as it is the closest option to the calculated wavelength of 2 cm.

A Michelson Interferometer Is Set Up for Microwaves