Question

when white light is incident normally on an oil film of thickness 10-4 cm and refractive index 1.4 then the wavelenght which will not be seen in the reflected system of light is ( in angstrom)




1) 7000




2) 5600




3) 4000




4) all of these

Answer 1

Like this for the wavelength which will not be seen

Answer 2

Explanation:

The thickness of film t=10^−4

cm=10^−6

m

The refractive index μ=1.4

For destructive interference in the reflected system

2μtcosr=(n+1)λ

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