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  • What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film <img alt="\mathrm{=1.5,}" src="https://en

What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film \mathrm{=1.5,} wavelength of the light incident on the film \mathrm{=600 \mathrm{~nm}.}

Option: 1

100 nm


Option: 2

300 nm


Option: 3

50 nm


Option: 4

200 nm


Answers (1)

Condition for constructive interference is \mathrm{2 \mu \mathrm{t}=(2 \mathrm{n}+1) \frac{\lambda}{2}}

Where, \mathrm{\mathrm{n}=0,1,2,3, \ldots \ldots}

For minimum thickness, \mathrm{\mathrm{n}=0}

\mathrm{ 2 \mu \mathrm{t}=\frac{\lambda}{2} \Rightarrow \mathrm{t}=\frac{\lambda}{4 \mu}=\frac{600 \times 10^{-9}}{4 \times 1.5}=100 \mathrm{~nm} }

Posted by

Ramraj Saini

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