If a source of power 4 kW produces 1020 photons/second, the radiation belongs to a part of the spectrum called

  1. microwaves
  2. X rays
  3. γ rays
  4. ultraviolet rays

Answer

P = 4000 W

E = hc/λ 

λ = hc x 1020 / 4000 = hc x 1017 / 4

λ = 3 x 108 x 6.6 x 10-34+17 / 4

= 19.8 x 10-9 / 4

= 4.9 x 10-9

λ = 49 X 10-10

≈ 49 Å

Since 0.1 Å < λ < 100 Å, It is X-ray

The correct option is B.

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