Question

A 360-nm thick oil film floats on the surface of the water. The indices of refraction of the oil and the water are 1.5 and 1.33, respectively. The surface of the oil is illuminated from above at normal incidence with white light. What TWO wavelengths of light in the 400-nm to 800-nm wavelength band are most strongly reflected

Answer 1

The correct answer is 432, and 720.

Step-by-step explanation:

The thickness of a film't' = 360nm

the refractive index of oil is given by

n₀t= (m +1/2) λ

->For m =0

λ = 4n₀t => 4(1.50)(360x
`10^-^9`)

λ= 2160nm

->for m = 1

λ = 4n₀t

= 4(1.50)(360)/3

= 720nm

-> for m = 2

λ = 4n₀t/5 = 4(1.50)(360)/5

= 432nm

The wavelength which are most strongly reflected are

432nm, 720nm.