## In This post you will get answer of Q.

Newton’s rings are observed. normally in reflected light of wavelength $5000 mathring A$

. The diameter of the 10$^{th}$ dark ring is 0.005 m. The radius of curvature of the lens is

Solution:

## Diameter of $n^{th}$ dark ring,

$D_n = 2 sqrt{n lambda R}$

$ therefore , , R = frac{D^2_n}{4n lambda}$

Here, $n = 10, D_{10} = 0.005 : m$

$ lambda = 5000 mathring A

= 5000 times 10^{-10} m = 5times 10^{-7} m$

$therefore R= frac{left(0.005 mright)^{2}}{4times 10times 5times 10^{-7}m} = 1.25 m $