Identify the correct statements.
(A) The energy (E) and momentum (p) of a photon are related by p = E/c.
(B) The electrons and photons of the same wavelength, possess the same momentum.
(C) One photon having energy more than work function can emit one photo electron.
(D) Photons do not carry momentum.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A), (B) and (C) only
(A) The energy (E) and momentum (p) of a photon are related by p = E/c. — Correct. For a photon \( E = h\nu \) and \( \lambda = c/\nu \), so \( p = h/\lambda = E/c \).
(B) The electrons and photons of the same wavelength, possess the same momentum. — Correct. The de Broglie relation \( p = h/\lambda \) holds for both, so for the same \( \lambda \) the momentum is the same.
(C) One photon having energy more than work function can emit one photo electron. — Correct. In the photoelectric effect one photon is absorbed by one electron, which escapes if the photon energy exceeds the work function.
(D) Photons do not carry momentum. — Incorrect. A photon has energy \( h\nu \) and momentum \( h/\lambda \), although it has no rest mass.
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.”
Einstein’s Photoelectric Equation: Energy Quantum of Radiation – “… In photoelectric effect, an electron absorbs a quantum of energy (hν) of radiation. If this quantum of energy absorbed exceeds the minimum energy needed for the electron to escape from the metal surface (work function φ0), the electron is emitted with maximum kinetic energy
\( \displaystyle K_{max} = h\nu - \phi_0 \qquad (11.2) \)”
Wave Nature of Matter – “… De Broglie proposed that the wave length λ associated with a particle of momentum p is given as
\( \displaystyle \lambda = \frac{h}{p} = \frac{h}{mv} \qquad (11.5) \)”