The Total solution for NCERT class 6-12
A100 W sodium lamp radiates energy uniformly in all directions. The lamp islocated at the centre of a large sphere that absorbs all the sodium light whichis incident on it. The wavelength of the sodium light is 589 nm. (a) What isthe energy per photon associated with the sodium light? (b) At what rate arethe photons delivered to the sphere?
Power of the sodium lamp, P =100 W
Wavelength of the emitted sodiumlight, λ = 589 nm = 589 × 10−9 m
Planck’s constant, h =6.626 × 10−34 Js
Speed of light, c = 3 × 108 m/s
(a)The energy per photonassociated with the sodium light is given as:
(b)Number of photonsdelivered to the sphere = n
Theequation for power can be written as:
Therefore, every second, photons are delivered to the sphere.