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(a) Write Einstein's photoelectric equation and mention which important features in photo-electric effect can be explained with the help of this equation. (b) The maximum kinetic energy of the photoelectrons gets doubled when the wavelength of light incident on the surface changes from lamda_(1) to lamda_(2). Derive the expressions for the threshold wavelength lamda_(0) and work function fo rthe metal surface. |
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Answer» Solution :(B) In terms of wavelength `LAMDA`, the photoelectric wavelength. As per question for incident LIGHT of wavelength `lamda_(1), K_(max)=K(say)` and for light of wavelength `lamda_(2),K_(max)=2K.` hence, we have `hc((1)/(lamda_(1))-(1)/(lamda_(0)))=K and hc((1)/(lamda_(2))-(1)/(lamda_(0)))=2K ` `implies 2((1)/(lamda_(1))-(1)/(lamda_(0)))=(1)/(lamda_(2))-(1)/(lamda_(0))implies (1)/(lamda_(0))=(2)/(lamda_(1))-(1)/(lamda_(2)) implies lamda_(0)=(lamda_(1)lamda_(2))/((2lamda_(2)-lamda_(1)))` and work function of the metal `phi_(0)=(hc)/(lamda_(0))=(hc(2lamda_(2)-lamda_(1)))/(lamda_(1)lamda_(2))`. |
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