Einstein's photoelectric equation is best written as 
A$h\nu = \phi_0 - K_{\max}$
B$h\nu = K_{\max}$
C$h\nu = \phi_0 + K_{\max}$
D$\phi_0 = h\nu + K_{\max}$
Answer & Solution
Correct answer: C. $h\nu = \phi_0 + K_{\max}$
Einstein explained that the incident photon energy $h\nu$ is used partly to overcome the work function $\phi_0$ and the remainder appears as maximum kinetic energy of the photoelectron. Hence $h\nu=\phi_0+K_{\max}$.

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