Question

A very sharp wedge of glass of index of refraction 1.50 is introduced perpendicularly in the path of one of the interfering beams
of Michelson interferometer illuminated by a narrow beam of light of
wavelength 0.500 ?m. This causes 600 dark fringes to sweep across the
field of view. Calculate the thickness of the glass wedge at the point
where the beam passes through it.

Answer 1

An interferometer measures the lengths or changes in length by means of interference of light fringes. As a material is inserted into the optical path of mirrors in interferometer, a shift in fringe pattern is observed in the interferometer.

This shift in number of fringes is given as,

where is number of fringes through which the material causes the pattern to shift

L is thickness of material used

n is refractive index of material

is wavelength of light

The thickness of wedge (L) from the above equation is given as,

using the given values to get,

is the the thickness of the glass wedge at the point where the beam passes through it.