InterviewSolution
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InterviewSolution
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A student performs an experiment on photoelectric effect,using two materials A and B.A plot V_("stop")vs v is given in figure. (i)Which material A or B has a higher work function? (ii)Given the electric charge of an electron=1.6xx10^(-19)C,find the value of the h obtained from the experiment for both A and B.Comment on whether it is consistent with Einstein's theory: |
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Answer» Solution :(i)Work function ,`phi_(0)=hf_(0)` (where `f_(0)`=threshold frequency) `therefore phi_(0)propf_(0)` ……..(1) From the figure , `f_(0)A=5XX10^(14)`Hz `f_(0)B=10xx10^(14)Hz` `impliesf_(0)Bgtf_(0)A` `IMPLIES` From relation(1), `phi_(0)Bgtphi_(0)A` (ii)We know that slope of graph of |`V_(0)|tof` Gives us value of `((h)/(e))`.HENCE Slope of graph for A, `tantheta_(1)=(PQ)/(QR)` `therefore (h)/(e)=(2)/(5xx10^(14))=0.4xx10^(-14)` `therefore h=0.4xx10^(-14)xxe` `therefore h=0.4xx10^(-14)xx1.6xx10^(-19)` `therefore h=6.4xx10^(-34)JS` .......(2) Slope of graph for B, `tantheta_(2)=(ST)/(QT)` `therefore (h)/(e)=(2.5)/(5xx10^(14))=0.5xx10^(14)` `therefore h=0.5xx10^(-14)xxe` `=0.5xx10^(-14)xx1.6xx10^(19)` `h=8xx10^(-34)Js` ..........(3) Thus ,here value of h are obtained different from the graphs for A and B.Hence ,above experimental observations are not consistent with Einstein.s theory. |
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