Question 25: NCERT Solutions for 12th Class Physics: Chapter 11-Dual Nature of Radiation and Matter
Estimating the following two numbers should be interesting. The first number will tell you why radio engineers do not need to worry much about ‘photons’. The second number tells you why our eye can never’eount photons’ even barely detectable light.
(a) The number of photons emitted per , second by a MW transmitter of 10 kW power emitting radio waves of length 500 m.
(b) The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can perceive (~ 10-10 W m-2). Take the area of the pupil ‘to be about 0.4 cm2 and the average frequency of white light to be about 6 × 1014 Hz.