Question

In a newton ring experiment what is the difference in diameter of 25th and 16th dark rings

Answer 1

Answer: The difference in diameter of 25th and 16th dark rings is equal to the diameter of first dark ring.

Explanation:

The diameter of a dark ring in Newton's ring experiment is:

$D_n=2\sqrt{n\lambda R}$

where n is the number of ring, \lambda is the wavelength of the light and R is the radius of curvature of convex lens.

For first dark ring:

$D_1=2\sqrt{\lambda R}$

For 25th dark ring:

$D_{25}=2\sqrt{25\lambda R}=5\times D_1$

For the 16th dark ring:

$D_{16}=2\sqrt{16\lambda R}=4\times D_1$

The difference between diameters of 25th and 16th dark rings is:

$D_{25}-D_{16}=5\times D_1-4\times D_1=D_1$

Hence, the difference in diameter of 25th and 16th dark rings is equal to the diameter of first dark ring.