Question

Problem 7: If a double-slit experiment were to be performed underwater, where the index of refraction for water is 1. 33,

instead in the air, where the index of refraction is 1. 00, how would the observed interference pattern be affected? Are the
fringes:
a) More closely spaced b) more widely spaced c) spaced the same as in air?
(Hint: Consider how light changes in a medium with a higher index of refraction. )

Answer 1

m λ = d sin θ describes the fringe pattern for a double slit

λ (water) = λ (air) / n = λ / 1.33

Thus the fringes would be more closely spaced.