Question

A thin film soap bubble (n=1.35) is floating in air. If the thickness of the bubble wall is 300nm, which of the following wavelengths of visible light is strongly reflected?

Answer 1

Answer:

540 nm

Explanation:

According to the question,

The refractive index of the soap bubble, $n=1.35$.

The thickness of the soap bubble wall is, $t=300 nm$.

Now, for constructive interference of soap bubble.

$2nt=(m+\frac{1}{2})\lambda$.

Now for first order m=1.

Therfore,

$\lambda =\frac{4}{3} tn$

Substitute all the variables in the above equation.

$\lambda =\frac{4}{3} (1.35)(300 nm)$.

Therefore,

$\lambda =540 nm$.

Therefore the visible light wavelength which is strongly reflected is 540 nm.