If the wavelength of an electromagnetic radiation is doubled, the energy of the photons would be
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → one half of its initial value
The energy of a photon is inversely proportional to the wavelength of the radiation, since \( c = \nu\lambda \).
\( \displaystyle E = h\nu = \frac{hc}{\lambda} \)
\( \displaystyle \frac{E'}{E} = \frac{\lambda}{\lambda'} = \frac{\lambda}{2\lambda} = \frac{1}{2} \)
So the photon energy becomes one half of its initial value.
NCERT (2026-27):
Particle Nature of Light: The Photon – “… (iii) All photons of light of a particular frequency ν, or wavelength λ, have the same energy \( E \;(= h\nu = hc/\lambda) \) and momentum \( p \;(= h\nu/c = h/\lambda) \), whatever the intensity of radiation may be.”