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What is the minimum thickness of a thin ...

What is the minimum thickness of a thin film `(mu=1.2)` that results in constructive interference in the reflected light? If the film is illuminated with light whose wavelength in free space is `lambda=500nm` ?

A

104 nm

B

200 nm

C

300 nm

D

400 nm

Text Solution

Verified by Experts

The correct Answer is:
A
For constructive interference in case of soap film
`2mut=(n-1/2)lambda (n-1,2,3,....)`
For minima thickness `t, n=1 or 2mut=lambda//2`
The minima thickness of a soap bubble
`t=lambda/(4mu)=500/(4xx12)=104.17 approx104nm`
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Knowledge Check

  • What is the minimum thickness of thin film required for constructive interference in the reflected light through it ? (Given, the refractive index of the film =1.5, wavelength of the lilght incident on the film =600 nm.

    A
    100 nm
    B
    50 nm
    C
    200 nm
    D
    25 nm

  • What is the minimum thickness of a soap bubble needed for constructive interference in reflected light if the light incident on the film has wavelengths 900 nm ? Assume the refractive index for the film is mu = 1.5

    A
    `100 nm`
    B
    `150 nm`
    C
    `200 nm`
    D
    `250nm`

  • What is the minimum thickness of a soap bubble needed for constructive interference in reflected light, if the light incident on the film is 750 nm? Assume that the refractive index for the film is n=1.33

    A
    282 nm
    B
    `70.5 nm`
    C
    141 nm
    D
    387 nm

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