Question

A thin film of transparent material in air has a refractive index of 1.50 and a thickness of 204 nm. For light incident normally on the film, take interference into account to predict which (if any) wavelength(s) of light in the visible portion of the spectrum (400 nm to 700 nm) will be transmitted through the film particularly: i): well
ii): poorly

Answer 1

Answer:

612 nm wavelength will be properly transmitted and 306 nm  wavelength will be poorly transmitted.

Explanation:

Given that,

Refractive index = 1.50

Thickness = 204 nm

We need to calculate the wavelength

For interference due to transmitted light

$2\mu t\cor r=m\lambda$

Here, r = 0° , for normal incidence

$2\mu t=m\lambda$

For m = 1

$2\times1.50\times204\times10^{-9}=1\times\lambda$

$\lambda=612\ nm$

For m = 2

$2\times1.50\times204\times10^{-9}=2\times\lambda$

$\lambda=\dfrac{2\times1.50\times204\times10^{-9}}{2}$

$\lambda=306\ nm$

Hence, 612 nm wavelength will be properly transmitted and 306 nm  wavelength will be poorly transmitted.