The fraunhofer diffraction pattern of a single slit is formed at the focal plane of a lens of focal length 1m. The width of the slit is 0.3 mm. if the third minimum is formed at a distance of 5 mm from the central maximum then calculate the wavelength of light.

Options

A. 5000 Å
B. 2500 Å
C. 7500 Å
D. 8500 Å

Answer

A

Explanation

`asintheta=nlamdarArr(ax)/f=3lamda`
(since `theta` is very small so `sintheta~~tantheta~~theta=x//f`)
or `lamda=(ax)/(3f)=(0.3xx10^(-3)xx5xx10^(-3))/(3xx1)`
= `5xx10^(-7)m=5000Å`