Rest mass of a photon is________________?
Correct answer: B. zero
- A. infinite
- B. zero
- C. very small
- D. 1.67 x 10^-27 kg
Explanation
A photon has zero invariant or rest mass, although it carries energy E = hf and momentum p = E/c. Rest mass is the mass measured in a particle's own rest frame, and a photon has no rest frame because it travels at light speed. Students may choose c by confusing its nonzero energy with nonzero rest mass.
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About Photons and the Particle Model of Light
The particle model treats light as photons with energy E equals hf and momentum related to wavelength. Questions involve the photoelectric effect, work function, threshold frequency, stopping potential and photon energy, while distinguishing particle behaviour from the wave description of interference and diffraction.
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