A 200 W sodium street lamp emits yellow light of wavelength 0.6 µm

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

(a) 1.5 x 10²⁰
(b) 6 x 10¹⁸
(c) 62 x 10²⁰
(d) 3 x 10¹⁹

Correct Answer:

1.5 x 10²⁰

Explanation:

Give that, only 25% ov 200 W converter electrical energy into light of yellow colour
(hc / λ) x N = 200 x 25/100
Where N is the no. of photons emitted per second, h = plank’s constant, c, speed of light
N = 200 x 25 / 100 x λ / hc
= 200 x 25 x 0.6 x 10⁻⁶ / (100 x 6.2 x 10⁻³⁴ x 3 x 10⁸)
= 1.5 x 10²⁰

admin:

Related Questions

  1. A nucleus disintegrates into two nuclear parts which have their velocities in the ratio
  2. Core of electromagnets are made of ferromagnetic material which has
  3. According to photon theory of light which of the following physical quantities,
  4. A juggler maintains four balls in motion,making each of them to rise
  5. The molar specific heats of an ideal gas at constant pressure and volume are denoted