Young's double slit experiment is first performed in air and then in a medium other than air. It is found that 8th bright fringe in the medium lies where 5th dark fringe lies in air. The refractive index of the medium is nearly
- 1.59
- 1.69
- 1.78
- 1.25
Answer
(3) 1.78
Solution
In the medium the wavelength becomes .
Position of the 8th bright fringe in the medium: y = 8 D d
Position of the 5th dark fringe in air: y = (2 5 - 1) D2d = 4.5 Dd
8 = 4.5
= 84.5 1.78
Answer: (3)