If h is the Planck's constant, then the momentum of a photon having frequency ν, is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → hν ÷ c
A photon of frequency \( \nu \) has energy \( E = h\nu \). By the energy-momentum relation for a photon (a particle with zero rest mass), its momentum is its energy divided by c.
\( \displaystyle p = \frac{E}{c} = \frac{h\nu}{c} \)
Since \( c = \nu\lambda \), this is the same as \( p = h/\lambda \), the de Broglie relation.
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.”