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JEE Mains · Physics · STD 12 - Dual nature of radiation and matter
  • JEE Mains 2022
  • Medium
  • MCQ

Let \(K_{1}\) and \(K_{2}\) be the maximum kinetic energies of photo-electrons emitted when two monochromatic beams of wavelength \(\lambda_{1}\) and \(\lambda_{2}\), respectively are incident on a metallic surface. If \(\lambda_{1}=3 \lambda_{2}\) then

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Answer & Solution

Correct Answer

(B) \(K _{1} < \frac{ K _{2}}{3}\)

Step-by-step Solution

Detailed explanation

\(\frac{ hc }{\lambda_{1}}-\phi= K _{1}\)

\(\frac{ hc }{\lambda_{2}}-\phi= K _{2}\)

\(\lambda_{1}=3 \lambda_{2}\)

\(3 K _{1}=\frac{3 hc }{\lambda_{1}}-3 \phi\)

\(3 K _{1}=\frac{h c }{\lambda_{2}}-3 \phi\)

\(3 K _{1}= K _{2}-2 \phi\)

\(3 K _{1}< K _{2}\)

\(K _{1}<\frac{ K _{2}}{3}\)

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