Q : In young’s double slit experiment the two slits are illuminated by light of wavelength 5890°A and the distance between the fringes obtained on the screen is 0.2°. If the whole apparatus is immersed in water then the angular fringe width will be, if the refractive index of water is 4/3

(a) 0.30°

(b) 0.15°

(c) 15°

(d) 30°

Ans: (b)

Sol:

Angular Width $ \displaystyle \theta ‘ = \frac{\theta}{\mu} $

$ \displaystyle \theta ‘ = \frac{0.2}{4/3} $

$ \displaystyle = \frac{0.6}{4} $

= 0.15°