When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectrons are liberated. For another emitter, however light of 600nm wavelength is sufficient for creating photoemission. What is the ratio of the work functions of the two emitters?
Correct answer: B. 2 : 1
- A. 1 : 2
- B. 2 : 1
- C. 4 : 1
- D. 1 : 4
Explanation
Since this question skips the part about the kinetic energy of the emitted electrons, we are to assume that the energy delivered by the photons has been entirely absorbed by the electrons to break free, thus the work function is equivalent to the energy provided. Work Function= Energy= hc/𝜆 The work function, through this formula, is inversely propotional to 𝜆; Work Function300nm : Work Function600 nm 1/300nm : 1/600nm Multiplying both sides by 600nm 600nm/300nm : 600nm/600nm 2 : 1
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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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