Physics Dawn of Modern Physics ETEA 2022
PMDC Verified Question 31 of 52
Which photon is travelling with largest speed in vacuum?
A
Gamma photon
B
Visible light photon
C
All photons move with the speed of light
D
Infrared
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: All photons move with the speed of light
Concept:

A fundamental postulate of electromagnetism and Special Relativity is the invariance of the speed of light for all massless particles in a vacuum.

Formula:

$$ c = 3 \times 10^8 \text{ m/s} $$

Solution:

  • Photons are the gauge bosons of the electromagnetic force and possess precisely zero rest mass.


  • Regardless of their frequency, energy, or position on the electromagnetic spectrum (gamma, visible, radio), all massless particles must travel at exactly \( c \) in a vacuum.


Why other options are incorrect:

Assuming higher energy (Gamma) translates to higher speed is a classical mechanics fallacy. Energy differences in photons appear as frequency shifts, not speed changes.

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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