The photosensitive surface is receiving the light of wavelength 5000   A ∘ at the rate of 10 - 8   J  s - 1 .  The number of photons received per second is ( h = 6 . 62 × 10 - 34   J   s ,   c = 3 × 10 8   m   s - 1 )

Step-by-step solution

Energy of photon E = h c λ Given, λ = 5000 Å = 5 × 10 - 7 m ∴ E = 6.6 × 10 - 34 × 3 × 10 8 5 × 10 - 7 = 3.96 × 10 - 19 J Energy received per second = 10 - 8 J s - 1 ∴ Number of photon's received per second = E n e r g y r e c e i v e d p e r s e c o n d E n e r g y o f o n e p h o t o n = 10 - 8 3.96 × 10 - 19 = 2.5 × 10 10