Which one of the following is massless?
Correct answer: D. Photon
- A. Proton
- B. Electron
- C. Neutron
- D. Photon
Explanation
A photon has zero rest mass, although it carries energy and momentum and travels at the speed of light in vacuum. The electron is the likely alternative because it is very light, but it still has a rest mass of about 9.11 x 10^-31 kg.
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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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