Question

A 100W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm.
(a) What is the energy per photon associated with the sodium light?
(b) At what rate are the photons delivered to the sphere?

Answer 1

Power of the lamp, P = 100 W
λ = 589 nm = 589 × 10^-9m
(a) Therefore, energy of a photon of sodium lamp light,

(b) The number of photons falling per second on the surface of the sphere,