The work functions for metals A, B and C are 1.92eV,2.0eV and 5.0eV respectively. According to Einstein’s equation, the metals which will emit photoelectrons for a radiation of wavelength 4100A∘ is/are
A
None
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B
A only
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C
A and B only
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D
All the three metals
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Solution
The correct option is C A and B only Einstein's equation is E=ϕ+K.E where E is the energy of incident radiation, ϕ is work function of metal and K.E is the kinetic energy of emitted electrons.
Thus for emission of photoelectrons, E≥ϕ In this case, energy of incident radiation E=hcλ=12431λ(in∘A)eV =124314100=3.03eV
E>ϕA and ϕB but E<ϕC So, electrons will be emitted from both A and B.