Which of the following statements related to photons of electromagnetic radiation are correct?
(A) Photon energy is independent of intensity of radiation.
(B) Photons are deflected by electric and magnetic fields.
(C) In a photon-electron collision, the total energy is conserved, but total momentum is not conserved.
(D) In a collision the number of photons may not be conserved. The photon may be absorbed, or a new photon may be created.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (D) only
In the photon picture, radiation of frequency \( \nu \) consists of photons of energy \( E = h\nu \) and momentum \( p = h\nu/c \); photons are electrically neutral.
(A) Photon energy is independent of intensity of radiation. — Correct. \( E = h\nu \) depends only on the frequency; a higher intensity means more photons per second, not more energetic photons.
(B) Photons are deflected by electric and magnetic fields. — Incorrect. Photons carry no charge, so electric and magnetic fields do not deflect them.
(C) In a photon-electron collision, the total energy is conserved, but total momentum is not conserved. — Incorrect. In a photon–electron collision both the total energy and the total momentum are conserved.
(D) In a collision the number of photons may not be conserved. The photon may be absorbed, or a new photon may be created. — Correct. Unlike energy and momentum, the number of photons is not conserved: a photon may be absorbed (as in the photoelectric effect) or a new photon may be emitted.
NCERT (2026-27):
Particle Nature of Light: The Photon – “… We can summarise the photon picture of electromagnetic radiation as follows:
(i) In interaction of radiation with matter, radiation behaves as if it is made up of particles called photons.
(ii) Each photon has energy \( E\,(=h\nu) \) and momentum \( p\,(=h\nu/c) \), and speed \( c \), the speed of light.
(iii) All photons of light of a particular frequency \( \nu \), or wavelength \( \lambda \), have the same energy \( E\,(=h\nu = hc/\lambda) \) and momentum \( p\,(=h\nu/c = h/\lambda) \), whatever the intensity of radiation may be. By increasing the intensity of light of given wavelength, there is only an increase in the number of photons per second crossing a given area, with each photon having the same energy. Thus, photon energy is independent of intensity of radiation.
(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. However, the number of photons may not be conserved in a collision. The photon may be absorbed or a new photon may be created.”