Question

Monochromatic light of wavelength 500 nm is used in Young's double slit experiment. An interference pattern is obtained on a screen When one of the slits is covered with a very thin glass plate (refractive index = 1.5), the central maximum is shifted to a position previously occupied by the \(4^{\text {th }}\) bright fringe. The thickness of the glass-plate is ……………….µm.

Answer 1

Correct answer is :  4 

When glass plate is insert, then the extra path difference will be  

\((\mu-1) \mathrm{t}=\mathrm{n} \lambda\) 

\((1.5-1) \mathrm{t}=4 \times 500 \times 10^{-9}\) 

\( \mathrm{t}=\frac{4 \times 500 \times 10^{-9}}{0.5}\) 

\( \mathrm{t}=4 \times 10^{-6}=4 \mu \mathrm{m}\)