JEE Main20199 Apr 2019Morning ShiftPhysicsAtomic PhysicsActual
Taking the wavelength of first Balmer line in hydrogen spectrum ( n = 3 to n = 2 ) as 660 n m , the wavelength of the 2 n d Balmer line ( n = 4 to n = 2 ) will be :
Options
- A889.2 n m
- B488.9 n m
- C388.9 n m
- D642.7   nm
Correct answer
B. 488.9 n m
Step-by-step solution
From Rydberg’s equation, 1 λ = R 1 n 2 - 1 n 2 2 1 660 × 10 - 9 = R 1 2 2 - 1 3 2 1 λ = R 1 2 2 - 1 4 2 λ 600 × 10 - 9 = 5 9 × 4 × 16 × 4 12 λ = 488.9 n m