AIPMT PRELIMS2012Physics-Optics
AIPMT PRELIMS 2012 Physics Photon Energy MCQ Question
Type: MCQ-numerical-Hard-Class 12
A 200 W sodium street lamp emits yellow light of wavelength 0.6 μm. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is
A
3 × 10¹⁹
B
1.5 × 10²⁰
C
6 × 10¹⁸
D
62 × 10²⁰
Correct Answer
Option B
Detailed Explanation
The energy emitted as light is 50 J/s. Using E = hc/λ, the number of photons is calculated as 1.5 × 10²⁰.
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