Subject: Applied Physics 2

Topic: Interference And Diffraction

Difficulty: Medium

For dark ring , $D_n^2 = 4nλR$,

$ D_{40}^2 = 4 \times 40 \times λ \times R$………………………………(1)

Let n$^{th}$ be the order of ring whose diameter is double the diameter of 40$^{th}$ dark ring .

$(2 D_{40} )^2 = 4 \times n \times λ \times R$……………………………….(2)

From equation 1 and 2,

$ \frac{D_{40}^2}{4D_{40}^2} = \frac{40}{n} $

Therefore n= 160