JEE Main201910 Jan 2019Morning ShiftPhysicsWave OpticsActual
In a Young's double slit experiment slit separation 0.1 m m , one observes a bright fringe at angle 1 40 r a d by using light of wavelength λ 1 . When the light of wavelength λ 2 is used a bright fringe is seen at the same angle in the same set up. Given that λ 1 and λ 2 are in visible range 380 n m t o 740 n m , their values are:
Options
- A400 n m , 500 n m
- B380 n m , 525 n m
- C625 n m , 500 n m
- D380 n m , 500 n m
Correct answer
C. 625 n m , 500 n m
Step-by-step solution
d s i n θ = n λ ∴ λ = d s i n θ n = 10 - 4 × 1 40 × 1 n ∴ λ = 2.5 × 10 - 6 n = 2500 × 10 - 9 n = 2500 n n m Putting n = 1 , λ 1 = 2500 n m n = 2 , λ 2 = 1250 n m n = 3 , λ 3 = 833 n m n = 4 , λ 4 = 625 n m n = 5 , λ 5 = 500 n m n = 6 , λ 6 = 357 n m