A metallic surface ejects photoelectrons when hit by green light but none when hit by yellow light. Will electrons be ejected if the same surface is hit by red light?
Correct answer: D. No
- A. Yes
- B. Yes, if the red beam is sufficiently intense
- C. Yes, if the red beam is allowed to fall for sufficient duration
- D. No
Explanation
Red light has less energy than yellow light, which itself is below the work function. So red light cannot cause photoemission.
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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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