K_1 and K_2 be the maximum kinetic energies of photoelectrons emitted from a surface of a given material for the light of wavelength λ_1 and λ_2 , respectively. If λ_1=2λ_2 then the work function of material is given by:

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Quantrex Academy · Accepted Answer

Correct answer: D. K_2-2K_1

Using Einstein's photoelectric equation:

K_1 = \dfrac{hc}{\lambda_1} - \phi

K_2 = \dfrac{hc}{\lambda_2} - \phi

Given

\lambda_1 = 2\lambda_2

, the first equation becomes:

K_1 = \dfrac{hc}{2\lambda_2} - \phi

Multiplying by

2

:

2K_1 = \dfrac{hc}{\lambda_2} - 2\phi

Substituting

\dfrac{hc}{\lambda_2} = K_2 + \phi

from the second equation:

2K_1 = (K_2 + \phi) - 2\phi

2K_1 = K_2 - \phi

\phi = K_2 - 2K_1

Answer:

K_2-2K_1

K_1 and K_2 be the maximum kinetic energies of photoelectrons...

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