2.48 In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of 3.15 × 10–18 J from the radiations of 600 nm, calculate the number of photons received by the detector.
From the expression of energy of one photon (E),
E =
Where, λ = wavelength of
radiation h = Planck’s
constant c = velocity of
radiation
Substituting the values in the given expression of E
E = = 3.313 × J
Energy of one photon = 3.313 × J
Number of photons received with 3.15 × J energy
=
= 9.5
≈ 10
