Physics-
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Question

If light of wavelength lambda subscript 1 end subscript is allowed to fall on a metal, then kinetic energy of photoelectrons emitted is E subscript 1 end subscript. If wavelength of light changes to lambda subscript 2 end subscript then kinetic energy of electrons changes to E subscript 2 end subscript. Then work function of the metal is

  1. fraction numerator E subscript 1 end subscript E subscript 2 end subscript left parenthesis lambda subscript 1 end subscript minus lambda subscript 2 end subscript right parenthesis over denominator lambda subscript 1 end subscript lambda subscript 2 end subscript end fraction    
  2. fraction numerator E subscript 1 end subscript lambda subscript 1 end subscript minus E subscript 2 end subscript lambda subscript 2 end subscript over denominator left parenthesis lambda subscript 1 end subscript minus lambda subscript 2 end subscript right parenthesis end fraction    
  3. fraction numerator E subscript 1 end subscript lambda subscript 1 end subscript minus E subscript 2 end subscript lambda subscript 2 end subscript over denominator left parenthesis lambda subscript 2 end subscript minus lambda subscript 1 end subscript right parenthesis end fraction    
  4. fraction numerator lambda subscript 1 end subscript lambda subscript 2 end subscript   E subscript 1 end subscript E subscript 2 end subscript over denominator left parenthesis lambda subscript 2 end subscript minus lambda subscript 1 end subscript right parenthesis end fraction    

The correct answer is: fraction numerator E subscript 1 end subscript lambda subscript 1 end subscript minus E subscript 2 end subscript lambda subscript 2 end subscript over denominator left parenthesis lambda subscript 2 end subscript minus lambda subscript 1 end subscript right parenthesis end fraction


    E = W0 + KmaxÞ fraction numerator h c over denominator lambda subscript 1 end subscript end fraction equals W subscript 0 end subscript plus E subscript 1 end subscript and fraction numerator h c over denominator lambda subscript 2 end subscript end fraction equals W subscript 0 end subscript plus E subscript 2 end subscript
    Þ h c equals W subscript 0 end subscript lambda subscript 1 end subscript plus E subscript 1 end subscript lambda subscript 1 end subscript and h c equals W subscript 0 end subscript lambda subscript 2 end subscript plus E subscript 2 end subscript lambda subscript 2 end subscript
    Þ W subscript 0 end subscript lambda subscript 1 end subscript plus E subscript 1 end subscript lambda subscript 1 end subscript equals W subscript 0 end subscript lambda subscript 2 end subscript plus E subscript 2 end subscript lambda subscript 2 end subscriptÞ W subscript 0 end subscript equals fraction numerator E subscript 1 end subscript lambda subscript 1 end subscript minus E subscript 2 end subscript lambda subscript 2 end subscript over denominator left parenthesis lambda subscript 2 end subscript minus lambda subscript 1 end subscript right parenthesis end fraction

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