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JEE Mains · Physics · STD 12 - Dual nature of radiation and matter
  • JEE Mains 2021
  • Medium
  • MCQ

An electron and proton are separated by a large distance. The electron starts approaching the proton with energy \(3\, {eV}\). The proton captures the electrons and forms a hydrogen atom in second excited state. The resulting photon is incident on a photosensitive metal of threshold wavelength \(4000\, \mathring {{A}}\). What is the maximum kinetic energy of the emitted photoelectron ? (In \({eV}\))

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Answer & Solution

Correct Answer

(C) \(1.41\)

Step-by-step Solution

Detailed explanation

Initially, energy of electron \(=+3 {eV}\)

Finally, in \(2^{\text {nd }}\) excited state,

\(E=-\frac{(13.6\, {eV})}{3^{2}}\)

\(=-1.51 \,{eV}\)

Loss in energy is emitted as photon,

So, photon energy \(\frac{{hc}}{\lambda}=4.51\, {eV}\)

No, photoelectric effect equation

\({KE}_{\max }=\frac{{hc}}{\lambda}-\phi=4.512-\left(\frac{{hc}}{\lambda_{{m}}}\right)\)

\(=4.51\, {eV}-\frac{12400\, {eV} \stackrel{\circ}{{A}}}{4000\, \stackrel{\circ}{{A}}}\)

\(=1.41\, {eV}\)

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