In photo-emission from a metal, if light of λ is replaced by light of wavelength λ / 4 , the maximum kinetic energy of the photoelectrons.
Correct answer: B. Increases by an amount equal to four times energy of an incident photon of wavelength λ
- A. Decreases by an amount equal to half of an incident photon of wavelength λ
- B. Increases by an amount equal to four times energy of an incident photon of wavelength λ
- C. Increases by an amount equal to the work function of the metal
- D. Decreases by an amount equal to the energy of an incident photon of wavelength λ
Explanation
The maximum kinetic energy KEe of ejected electrons (photoelectrons) is given by KEe=hf−BE , where hf is the photon energy and BE is the binding energy (or work function) of the electron to the particular material.Since f = v/ λ when λ is replaced by λ/4 , f increases by 4 times and hence the energy of incident photons increases by 4 times.
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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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