Light of a certain wavelength and intensity ejects photoelectrons from a metal plate. Then this beam is replaced by another beam of smaller wavelength and smaller intensity. As a result:
Correct answer: D. K.E of the photoelectrons decreases but the strength of the photoelectric current decreases
- A. No change occurs
- B. The emission of photoelectrons stops
- C. K.E of the photoelectrons decreases but the strength of the photoelectric current increases
- D. K.E of the photoelectrons decreases but the strength of the photoelectric current decreases
Explanation
This is a plausible scenario. If the new light has a smaller wavelength (higher energy) and smaller intensity, the kinetic energy of the ejected photoelectrons may decrease, but the overall current might also decrease due to the reduced number of photoelectrons. The photoelectric effect can be described using the following formula:E=hc/λ−ϕwhere E is the kinetic energy of the emitted photoelectronsh is Planck's constant (6.626×10−34J⋅s),c is the speed of lightλ is the wavelengthϕ is the work function of the material (the minimum energy required to remove an electron from the surface).
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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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