A certain light beam consists of n photons crossing per unit area per sec with energy E each and
linear momentum p each.
How will these three values, (n, E and p) change if
(i) intensity is doubled and frequency kept constant.
(ii) intensity is kept constant and frequency becomes double?

  Dear Student

Intensity if incident radiations I  = nhν
where
n   is number of photons
h is planck's constant
ν is frequency of radiation

So when intensity is doubled and frequency kept constant then number of photons also gets doubled. But energy and momentum of photon remains same as it is for each photon.

When intensity remains constant and frequency is doubled  then number of photons gets halved. ​ But energy and momentum of photon remains same as it is for each photon

Regards