Question 2.6: Find the energy of each of the photons

Question 2.6: Find the energy of each of the photons which
(i) corresponds to light of frequency 3× 10¹⁵ Hz.
(ii) have a wavelength of 0.50 Å.

Ans 2.6. We know
(i) Energy (E) of a photon (E) = hν —————–A
Where, h = Planck’s constant = 6.626 × 10^–34 Js
ν = frequency of light = 3 × 10¹⁵ Hz
ν = 3 × 10¹⁵ s^–1
Substituting the values of h and ν in expression A
E = (6.626 × 10^–34) (3 × 10¹⁵)
E = 1.988 × 10^–18 J

(ii) Energy (E) of a photon having wavelength (λ)is given as
E = hc/λ ———————–A
h = Planck’s constant = 6.626 × 10^–34 Js
λ = 0.50 × 10^-10m
c = velocity of light in vacuum = 3 × 10⁸ m/s
Substituting the values in the relation A
E = (6.626 × 10^–34) × 3 × 10⁸/ 0.50 × 10^-10m
E = 3.98 × 10^-15 J.