BITSAT2019PhysicsWave OpticsActual
In Young's double-slit experiment, the distance between slits and screen is 2 m and distance between slits is 0 . 25 mm . A light of wavelength 800 nm is used to find fringes on the screen. If the screen moves with a speed of 5 m s - 1 , then first maxima will move with a speed of:
Options
- A16   mm   s - 1
- B8   mm   s - 1
- C20   mm   s - 1
- D50   mm   s - 1
Correct answer
A. 16   mm   s - 1
Step-by-step solution
Given, D = 2   m ,   d = 0 . 25   mm = 2 . 5 × 10 - 4   m Velocity of screen, d D d t = 5   m   s - 1 Speed of first maxima = d β d t = ? In Young's double-slit experiment, fringe width β = D λ d On differentiating with respect to t , we get d β d t = λ d · d D d t = 800 × 10 - 9 2 . 5 × 10 - 4 × 5 = 16 × 10 - 3   m   s - 1 = 16   mm   s - 1