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:

Options

• 1.5 × 10²⁰

• 6 × 10¹⁸

• 62 × 10²⁰

• 3 × 10¹⁹

Answer 1

1.5 × 10²⁰