Question 2.11: A 25-watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.

Question 2.11: A 25-watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.

Question 2.11: A 25-watt bulb emits monochromatic yellow light of wavelength of 0.57µm. Calculate the rate of emission of quanta per second.
Answer 2.11: Power of bulb, P = 25 Watt = 25 Js^–1
The energy of one photon, E = hν = hc/Λ
Substituting the values of h, c, and Λ in the above relation
E = (6.626 × 10^-34) (3 × 10⁸)/0.57 × 10^-6
E = 34.87 × 10^–20 J
Rate of emission of quanta per second = Power/ Energy
= 25 Js^-1/34.87 × 10^–20 J = 7.169 × 10¹⁹ s^-1