NTA Abhyas JEE Main2020PhysicsWave OpticsPractice
White light is used to illuminate the two slits in Young's double-slit experiment. The separation between the slits is d and the distance between the slits and screen is D d ≪ D . At a point on the screen directly in front of one of the slits, certain wavelengths are missing. The missing wavelengths are
Options
- Aλ = d 2 D n - 1
- Bλ = d 2 D 2 n - 1
- Cλ = d 2 D n
- Dλ = d 2 D n
Correct answer
B. λ = d 2 D 2 n - 1
Step-by-step solution
The n t h order dark fringe is at a distance y n from the control zero-order bright fringe where y n = n + 1 2 λ D d , Here, n = 0 , 1 , 2 ......etc. y n = n - 1 2 λ D d , Here n = 1,2 .......etc. For the point on the screen directly infront of one of the slits, y n = d 2 . So, d 2 = n - 1 2 λ D d ⇒ λ = d 2 D 2 n - 1