MHT CET202620 April 2026Morning ShiftPhysicsWave OpticsActual
In an interference experiment, the m^ th bright fringe for light of wavelength ₁ coincides with the n^ th dark fringe for light of wavelength ₂ . The ratio ₂ ₁ is
Options
- Am n-1
- Bm (2n-1)
- C2m (2n-1)
- D2m (2n+1)
Correct answer
C. 2m (2n-1)
Step-by-step solution
The position of the m^ th bright fringe for light of wavelength ₁ is given by: y₁ = m ₁ D d The position of the n^ th dark fringe for light of wavelength ₂ is given by: y₂ = (2n - 1) ₂ D 2d Since the two fringes coincide, we equate their positions ( y₁ = y₂ ): m ₁ D d = (2n - 1) ₂ D 2d m ₁ = (2n - 1) ₂ 2 ₂ ₁ = 2m 2n - 1 Answer: 2m (2n-1)