Physics

Physics · optics

Problem

Example 35: A Newton's ring arrangement is used with a source emitting two wavelengths

\lambda_{1}=6 \times 10^{-5} \mathrm{~cm}

and

\lambda_{2}=4.5 \times 10^{-5} \mathrm{~cm}

and it is found that the

n^{\text {th }}

dark ring due to

\lambda_{1}

coincides with

(n+1)^{\text {th }}

dark ring due to

\lambda_{2}

. If the radius of curvature of the curved surface is 90 cm , find the diameter of the

n^{\text {th }}

dark ring for

\lambda_{1}