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A student performs an experiment on photoelectric effect, using two materials A and B. A plot of Vstop versus v is given in figure.

Answers (1)

We know that \phi_{0}=hv_{0}  where v0=Threshold frequency  

\frac{\phi_{0A}}{\phi_{0B}}=\frac{hv_{0A}}{hv_{0B}}=\frac{5*10^{14}}{10*10^{14}}=\frac{1}{2}\\ So\;\phi_{0B}=2\phi_{0A}

  (ii) By the differentiation of potential

V=\frac{W}{Q}

hv=eV

  Differentiating both the sides we get h.dv=edV

 h=\frac{edV}{dv}

 Using this formula

 For metal A, h=6*10-34Js….(i) 

For metal B, h=0.8*10-33…(ii)

 Since the value of plank'sconstant is not equal for both the experimental graphs, the experiment inconsistent with Einstein's theory. But the values are very close to 6.6*10-34Js  due to experimental limitation and hence can be considered consistent with Einstein theory.

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