Describe Applications of Newton’s Rings - QS Study
QS Study

Applications of Newton’s rings

(i) Using the method of Newton’s rings, the wavelength of a given monochromatic source of light can be determined. The radius of nth dark ring and (n+m)th dark ring are given by

rn2 = nRλ and r2n+m = (n+m) Rλ

rn+m2 – rn2 = mRλ

so, λ = [rn+m2 – rn2] / mR

Knowing rn+m, rn and R, the wavelength can be calculated.

 

(ii) Using Newton’s rings, the refractive index of a liquid can calculated. Let λa and λm represent the wavelength of light in air and in medium (liquid). If rn is the radius of the nth dark ring in air and if rn is the radius of the nth dark ring in liquid, then

rn2 = nRλa

r`n2 = nRλm = nRλa

so, μ = rn2/ r`n2