If the movable mirror in a Michelson interferometer is moved 120 microns, how many fringes would be counted for 600 nm light?
A)200
B)720
C)100
D)300
E)400

Question

Quizplus · Accepted Answer

The number of fringes counted is equal to the number of wavelengths that fit into twice the distance the mirror is moved. For a 120 micron movement, the path difference is 240 microns. Dividing 240,000 nm by 600 nm gives 400 fringes.

If the Movable Mirror in a Michelson Interferometer Is Moved