Dual Nature of Matter

JEE Main level, single correct, medium

124 of 200

Question 124 of 200

The work function of a substance is 3.0eV3.0eV. The longest wavelength of light that can cause the emission of photoelectrons from this substance is approximately:

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Answer: (B) 414nm414nm

For longest wavelength, the emitted electron will have nearly zero kinetic energy.
Therefore,
λ=hcWe\lambda =\dfrac{hc}{{W}_{e}}
⇒λ=1240nm−eV3eV\Rightarrow \lambda =\dfrac{1240nm-eV}{3eV}
⇒λ=413.33nm\Rightarrow \lambda =413.33nm
⇒λmax⁡≈414nm\Rightarrow {\lambda }_{\max }\approx 414nm

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