Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. If the frequency is halved and intensity doubled, the photoelectric current becomes:
Correct answer: D. Zero times the original current
- A. 4 times the original current
- B. 2 times the original current
- C. Half the original current
- D. Zero times the original current
Explanation
Original frequency = 1.5v₀. Halving gives 0.75v₀, which is below the threshold frequency v₀, so no photoelectrons are emitted, regardless of intensity.
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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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