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Wave Optics

Question
CBSEENPH12038506

Ultraviolet radiations of different frequencies v1 and v2 are incident on two photosensitive materials having work functions W1 and W2 (W1 > W2) respectively. The kinetic energy of the emitted electrons is same in both the cases. Which one of the two radiations will be of higher frequency? 

Solution

Given, the kinetic energy of the emitted electrons is same in both cases.

Kinetic energy is given by, 
                           K.E.  = hv-ϕ 

ν is the frequency of radiation and ϕ is the work function of materials.
Therefore, as per given, 

                    K.E. = hv1-W1                    hv1 = K.E. + W1

and,
                              K.E. = hv2-W2                            hv2 = K.E.+W2


 Given that,  W1 > W2 
Thus,    v1 > v2.

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