A hair is placed at one edge between two flat glass plates 7.32 cm long. When this arrangement is illuminated with 632 nm light, 130 bands are counted, starting at the point of contact of the two plates. How thick is the hair

The thickness of the hair is 4.0764x10^-5 m

Explanation:

2t=mL (L is wavelength)

2t = 129x632 (124 is used because m starts at 0)

2t = 81528

t = 40764

t = 4.0764x10^-5 m

If a phase shift occur, then we use;

2t = (m + 1/2)L and

2t = (129 + 1/2)632

2t = 81844

t = 40922

t = 4.0922x10^-5 m

The answers are almost the same.