Question

In a Young's double-slit experiment, the intensity at a point where the path difference is `lambda/3` (`lambda` being the wavelength of the light used) is I. If I₀ denotes the maximum intensity, then `"I"/"I"_0` is equal to ______.

Options

• `1/sqrt2`

• `sqrt3/2`

• `1/4`

• `3/4`

Answer 1

In a Young's double-slit experiment, the intensity at a point where the path difference is `lambda/3` (`lambda` being the wavelength of the light used) is I. If I₀ denotes the maximum intensity, then `"I"/"I"_0` is equal to `1/4`.

Explanation:

 `"I"/"I"_0` = cos² `(phi/2)`;

phase difference = `(2pi)/lambda xx` path difference

`phi = (2pi)/lambda Deltax = (2pi)/lambda xx lambda/3 =(2pi)/3`

∴  `"I"/"I"_0` = cos² `(pi/3)= "I"_0/4`