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JEE Main 2016 (10 Apr, Shift 1) · Photoelectric Effect: Einstein's Equation

Photoelectric Effect: Einstein's Equation question from JEE Main 2016 (10 Apr, Shift 1)

Q142JEE Main 2016 · 10 APR · SHIFT 1Medium

Photoelectric Effect: Einstein's Equation

A photoelectric surface is illuminated successively by monochromatic light of wavelengths $\lambda$ and $\frac{\lambda}{2}.$ If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface is:

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Answer: (b)

$K = \frac{hc}{\lambda} - \phi$ ; write $A = \frac{hc}{\lambda}$ .
First: $K_1 = A - \phi$ ; second ( $\lambda/2$ ): $K_2 = 2A - \phi$
$2A - \phi = 3(A - \phi) \Rightarrow 2\phi = A$
So the answer is (b) $\phi = \frac{hc}{2\lambda}$ .

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