Question

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) 1.5 x 10²⁰

(b) 6 x 10¹⁸

(c) 62 x 10²⁰

(d) 3 x 10¹⁹

Answer 1

The correct option is (a) 1.5 x 10²⁰.

Explanation:

Energy of a photon,