According to photon picture of electromagnetic radiation, which of the following statements is incorrect?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → In a photon-electron collision, the total energy and total momentum are not conserved.
In the photon picture, radiation consists of particles (photons) of energy \( E = h\nu \) and momentum \( p = h\nu/c \). Photons are uncharged, travel at \( c \) in vacuum, and in a collision with an electron they obey the conservation of energy and momentum (the number of photons may change, but the total energy and total momentum stay the same).
Option (1) Each photon has energy and momentum. — A correct statement. Each photon has \( E = h\nu \) and \( p = h/\lambda \).
Option (2) Each photon moves with speed of light in vacuum. — A correct statement. All photons travel at \( c = 3\times10^{8}\,\mathrm{m\,s^{-1}} \) in vacuum.
Option (3) Photons are electrically neutral. — A correct statement. Photons carry no charge, so electric and magnetic fields do not deflect them.
Option (4) In a photon-electron collision, the total energy and total momentum are not conserved. — The incorrect statement. Total energy and total momentum are conserved in a photon-electron collision.
NCERT (2026-27):
Particle Nature of Light: The Photon – “… We can summarise the photon picture of electromagnetic radiation as follows: … (ii) Each photon has energy E (= hν) and momentum p (= hν/c), and speed c, the speed of light. … (iv) Photons are electrically neutral and are not deflected by electric and magnetic fields. (v) In a photon-particle collision (such as photon-electron collision), the total energy and total momentum are conserved.”