Q. A double slit apparatus is immersed in a liquid of refractive index 1.33. It has slit separation of 1mm and distance between the plane of slits and screen 1.33m. The slits are illuminated by a parallel beam of light whose wavelength in air is 6300Å. The fringe width is
(a)(1.33×0.63)mm
(b) 0.63/1.33 mm
(c)0.63/(1.33)² mm
(d) 0.63 mm
Ans: (d)
Fringe Width $\large \beta = \frac{\lambda D}{\mu d} $
$\large \beta = \frac{6300 \times 10^{-10}\times 1.33}{1.33 \times 1 \times 10^{-3}} $
= 0.63 mm