InterviewSolution
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InterviewSolution
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Light of wavelength `lambda_(ph)`falls on a plate a vacum teke as shown in the figure .The work function of the conducting meterial kept at a distance d from the cathon A petential different V is maximum between the electrodes if the minimum de Brogle waveleeength of the electrons passing through the anode is `lambda_(e) ` which of the following statement (s) is (are) true? A. `lambda_(e)`decrease with increase in `phi and lambda_(ph)`B. `lambda_(e)` is approximentily balved , if d is doubledC. for large potential diffrence `(Vgtgt phi //e). Lambda_(e) `is approximately halved if V is made four timeD. `lambda_(e) ` increase at the same rate as `lambda_(ph) for lambda_(ph) lt hc//phi` |
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Answer» Correct Answer - C The wavelength of emitted photoelectron as per de brogher is ` lambda_(0) = (h)/(p) = (h)/(sqrt(2m (K.E))` when `lambda_(ph) increases N_(ph) decreases ` K.E. decreases and therefore I,e increse let is independent of the decreases d `Also(hc)/(lambda_(ph)) + eV - phi = (h^(2))/(2m lambda_(00)^(2)) [lambda = (h)/(sqrt(2mK . E))]` `:. (hc)/(e lambda_(ph)) + V (ph)/(e) = (b^(2))/(2me lambda_(0)^(2)))` ....(i) `for V gtgt (phi)/(e) , phi ltlt eV` ` also (hc)/(e lambda_(ph)) ltlt V ` Then from eq (i) `lambda_(e) prop (1)/(sqrt(V))` Therefore if V is mode our times `lambda_(e)` is approximated half |
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