NTA Abhyas JEE Main2020PhysicsWave OpticsPractice
A thin plastic sheet of refractive index 1.6 is used to cover one of the slits, among the two slits, in a double-slit arrangement. The central point on the screen is now occupied by what would have been the 7 t h bright fringe before the thin plastic sheet was used. If the wavelength of light is 600 nm , the thickness (in μm ) of the thin plastic sheet is
Options
- A7
- B4
- C8
- D6
Correct answer
A. 7
Step-by-step solution
The change in path = μ - 1 t . This path length change the position of bright fringe upto seventh bright fringe. t ( μ − 1 ) = 7 λ t = 7 ( 600 × 10 − 9 ) ( 1.6 − 1 ) = 7 × 10 − 6   m           ⇒ 7   μm