The mass of a photon at rest is:
Correct answer: D. Zero
- A. 1 amu
- B. 9 x 10^-31 kg
- C. 1.67 x 10^-35 kg
- D. Zero
Explanation
The rest mass of photon is zero. The mass of any particle at rest (relative to the observer) is known as the rest mass of that particle. One of the consequences of the Einstein's special theory of relativity is that the mass of the particle increases with increasing velocity relative to the observer. Since the photons are bound to travel at the speed of light (again a consequence of Einstein's special theory of relativity), a non-zero rest mass would lead to an infinitely massive particle.
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Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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