Question

In Young's double-slit experiment, in an interference pattern, a second minimum is observed exactly in front of one slit. The distance between the two coherent sources is 'd' and the distance between source and screen is 'D'. The wavelength of the light source used is ______

Options

• `"d"^2/"D"`

• `"d"^2/(2"D")`

• `"d"^2/(3"D")`

• `"d"^2/(4"D")`

Answer 1

In Young's double-slit experiment, in an interference pattern, a second minimum is observed exactly in front of one slit. The distance between the two coherent sources is 'd' and the distance between source and screen is 'D'. The wavelength of the light source used is `underline("d"^2/(3"D"))`.

Explanation:

The second minimum is exactly in front of one slit indicates, `"y"_2^' = "d"/2`

But `"y"_2^' = ((2"n" - 1)lambda"D")/(2"d")`

For n = 2

∴ `"d"/2 = ((2 xx 2 - 1)lambda"D")/(2"d")`

∴ `lambda = "d"^2/(3"D")`