Efficient power P=tN×λhc=200×0.25 tN=50×hcλ=6.6×10−34×3×10850×0.6×10−6=1.5×1020
A 200 ~W sodium street lamp emits yellow light of wavelength 0.6 μ m. Assuming it to be 25 % efficient in converting electrical energy to light, the…
NEET UG 2012 — Physics Modern Physics
2012mcqeasy
A 200 W sodium street lamp emits yellow light of wavelength 0.6μm. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is
Official previous-year question
Held on 30 Apr 2012 · Verified 9 Jul 2026.
Options
- A
1.5×1020
- B
6×1018
- C
62×1020
- D
3×1019
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