If h is the Planck's constant, then the momentum of the photon having frequency \( \nu \) is represented by
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( h\nu/c \)
The energy of a photon is \( E = h\nu \), and for a massless particle the energy and momentum are related by \( E = pc \).
\( \displaystyle p = \frac{E}{c} = \frac{h\nu}{c} \)
This is the same as \( p = h/\lambda \), because \( \lambda = c/\nu \).
Shortcut: Check the units. \( h\nu \) is an energy (\( \mathrm{kg\,m^2\,s^{-2}} \)) and \( c \) is a speed (\( \mathrm{m\,s^{-1}} \)), so \( h\nu/c \) has the unit \( \mathrm{kg\,m\,s^{-1}} \) of momentum. The other three options do not have this unit.
Note: This question is from NCERT (2026-27). NTA sets numerical questions from NCERT too, so do not ignore NCERT while practising numericals.
NCERT (2026-27):
Particle Nature of Light: The Photon – “… (ii) Each photon has energy E (=hν) and momentum p (= hν/c), and speed c, the speed of light.”