Ablue-green photon (λ = 488 nm ) is absorbed by a free hydrogen atom, initially at rest. what is the recoil speed of the hydrogen atom after absorbing the photon?

The recoil speed is

Solution:

Wavelength of a blue-green photon,

Now, the energy associated with the blue-green photon:

where

h = Planck's constant

C = speed of light ion vacuum

Also, we know that the recoil speed can be calculated by the KInetic energy which is equal to the Energy of the blue-green photon:

where

= velocity of Hydrogen atom

= mass of H-atom

Now,

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.