Solved UPSC CDS/OTA Question
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Q · Modern PhysicsMedium · 45s
The rest mass of a photon is — Option: 4
TopicModern Physics
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
The complete worked solution.
Every step explained - no skipped algebra.
A photon is massless when at rest; its energy is purely kinetic due to motion.
4
Final Answer: Option A - Zero
4