# Photoelectric emission is observed from a metal surface with incident frequencies v_(1) and v_(2) where v_(1) gt v_(2). If the kinetic energies of

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Photoelectric emission is observed from a metal surface with incident frequencies v_(1) and v_(2) where v_(1) gt v_(2). If the kinetic energies of the photoelectrons emitted in the two cases are in the ratio 2 : 1, then the threshold frequency v_(0) of the metal is
A. v_(1) = v_(2)
B. (v_(1) - v_(2))/(h)
C. 2 v_(1) - v_(2)
D. 2v_(2) - v_(1)

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hv_(1) = hv_(0) + E (K.E)..(i)
hv_(2) = hv_(0) + (1)/(2) E or 2 hv_(2) = 2 hv_(0) + E...(ii)
Eqn. (i) - Eqn (ii) gives hv_(1) - 2hv_(2) = hv_(0) - 2 hv_(0)
or v_(1) - 2 v_(2) = - v_(0) or v_(0) = 2 v_(2) - v_(1)