The slits in a double-slit interference experiment are illuminated by orange light `(lambda = 60 nm)`. A thin transparent plastic of thickness t is placed in front of one of the slits. The nunber of fringes shifting on screen is plotted versus the refractive index `mu` of the plastic in graph shown in figure. The value of t is

Options

A. `8.8 mm`
B. `649 mu m`
C. `24 mu m`
D. `600 nm`

Answer

C

Explanation

`N= (t/lambda)mu-(t)/(lambda)` which is a straight line
Slope of the line is `(t)/(lambda)`
`(t)/(600xx 10^(-9)m)= (40)/((2.00-1.00))" or "t= 24 mu""m`.