Modern Physics 2 Question 26

25. The threshold wavelength for photoelectric emission from a material is 5200\AA. Photoelectrons will be emitted when this material is illuminated with monochromatic radiation from a

(1982, 3M)

(a) 50W infrared lamp

(c) 50W ultraviolet lamp

(b) 1W infrared lamp

(d) 1W ultraviolet lamp

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Solution:

  1. For photoemission to take place, wavelength of incident light should be less than the threshold wavelength. Wavelength of ultraviolet light <5200\AA while that of infrared radiation > 5200\AA.


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