Subject: Applied Physics 2

Topic: Interference And Diffraction

Difficulty: Medium

Newtons rings are formed in the reflected light of $\lambda$ = 5859 $\mathring{A}$ with a liquid of RI = 1.33 between the plate & a lens having radius of curvature 113.5 cm. Find the diameter of the $5^{th}$ bright ring.

μ = 1.33, R = 113.5 cm, D$_5$ = ?, λ= 5859 x 10$^{-8}$

$ D_n^2 = \frac{4 R(2n±1)λ}{2μ} \\[2ex] D_5^2 = \frac{4 \times 113.5 (2 \times 5+1)5859 \times 10^{-8}}{2 \times 1.33} \\[2ex] D_5 = 0.33 cm $