The minimum energy required by a photo to create an electron-positron pair is:
Correct answer: C. 1.02 Mev
- A. 3 Mev
- B. 4 Mev
- C. 1.02 Mev
- D. Zero
Explanation
The mass m of a single electron is equivalent to 0.511 million electron volts (MeV) of energy E as calculated from the equation formulated by Albert Einstein, E = mc^2, in which c is the speed of light. To produce two electrons, therefore, the photon energy must be at least 1.022 MeV. Photon energy greater than this amount, when pair production occurs, is converted into motion of the electron-positron pair.
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About Dawn of Modern Physics
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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