All electrons ejected from a surface by incident light of wavelength 200 nm can be stopped before travelling 1 m in the direction of a uniform electric field of 4N/C. The work function of the surface is:
Correct answer: D. 2.2 eV
- A. 4eV
- B. 6.2 eV
- C. 2 eV
- D. 2.2 eV
Explanation
This value makes the maximum possible kinetic energy 6.2−2.2=4.0 eV, exactly the energy the field (4 V over 1 m) can remove. Thus all emitted electrons can be stopped within 1 m, matching the experiment.This is the following solution:
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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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