12th Class Physics Sample Paper Physics Sample Paper-7

  • question_answer
    Green light ejects photoelectrons from a given photosensitive surface whereas yellow light does not. What will happen in case of
    (i) violet, and     
    (ii) red light?
    Give reason for your answer.

    Answer:

    As photoelectric emission takes place for green light but does not take place for yellow light. Hence, threshold wavelength \[{{\lambda }_{0}}\] lies somewhere between them.

    (i) When incident light is of violet colour, its wavelength is even less than that of green light, i.e. \[\lambda <{{\lambda }_{0}},\] as a result, photoelectric emission will definetly take place.
    (ii) When incident light is of red colour, its wavelength is even greater than that of yellow light, i.e. \[\lambda >{{\lambda }_{0}},\] consequently, no photoelectric emission will take Place.


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