Three identical soap films ( ) in air have thicknesses ,

PHYSICS · Single correct · A Level · Physics · Waves · Waves

Problem

Three identical soap films (

n=1.33

) in air have thicknesses

t_1=\frac{\lambda}{4n}

t_2=\frac{\lambda}{2n}

, and

t_3=\frac{3\lambda}{4n}

, where

\lambda

is the wavelength of normally incident light in vacuum. Which ranking correctly orders the reflected intensity at wavelength

\lambda

from greatest to least? (a)

t_3 > t_1 > t_2

(b)

t_1 = t_3 > t_2

(c)

t_2 > t_1 = t_3

(d)

t_1 > t_3 > t_2