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JEE Advanced · Chemistry · 2. Atomic Structure

The work function ( \(\Phi\) ) of some metals is listed below. The number of metals which will show photoelectric effect when light of \(300 \mathrm{~nm}\) wavelength falls on the metal is

  1. A 2
  2. B 4
  3. C 6
  4. D 8
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Answer & Solution

Correct Answer

(B) 4

Step-by-step Solution

Detailed explanation

Energy of photon \(=\frac{h c}{\lambda} \mathrm{J}=\frac{h c}{e \lambda} \mathrm{eV}=\frac{6.625 \times 10^{-34} \times 3 \times 10^8}{300 \times 10^{-9} \times 1.602 \times 10^{-19}}=4.14 \mathrm{eV}\)
For photoelectric effect to occur, energy of incident photons must be greater than work function of metal. Hence, only \(\mathrm{Li}, \mathrm{Na}, \mathrm{K}\) and \(\mathrm{Mg}\) have work functions less than \(4.14 \mathrm{~V}\).
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