Physics Dawn of Modern Physics KU 2024
PMDC Verified Question 4 of 52
The momentum of moving photon is:
A
\( mc^2 \)
B
\( \frac{\lambda}{h} \)
C
\( \frac{h}{\lambda} \)
D
Zero
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \( \frac{h}{\lambda} \)
Concept:

Despite having no resting mass, a moving photon carries momentum as a consequence of relativistic energy-momentum dynamics.

Formula:

$$ p = \frac{E}{c} = \frac{hf}{c} = \frac{h}{\lambda} $$

Solution:

  • Using de Broglie's foundational wave-particle relation, momentum is definitively given as Planck's constant divided by the particle's wavelength.


  • Thus, \( p = \frac{h}{\lambda} \) perfectly describes photon momentum.


Why other options are incorrect:

\( mc^2 \) represents rest-mass energy, not momentum (and photons have no rest mass anyway). "Zero" momentum would mean the photon carries no energy and exerts no radiation pressure, which is false.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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