Q. The transition from the state n = 3 to n = 1 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from :
A) 2 → 1
B) 3 → 2
C) 4 → 2
D) 4 → 3
Explanation
[Solution from source] Infrared needs a much smaller energy gap than the ultraviolet 3 → 1 line. The energy factors (1/n₁² − 1/n₂²) are 3/4 for 2 → 1, 5/36 for 3 → 2, 3/16 for 4 → 2 and only 7/144 for 4 → 3, so 4 → 3 (Paschen-type) is the infrared one; 3 → 2 and 4 → 2 are visible for hydrogen. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.