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Thermal Radiation. Quantum Nature of Light.

Problem 5.274

Illuminating the surface of a certain metal alternately with light of wavelengths \(\lambda_{1}=0.35 \mu \mathrm{m}\) and \(\lambda_{2}=0.54 \mu \mathrm{m},\) it was found that the corresponding maximum velocities of photoelectrons differ by a factor \(\eta=2.0 .\) Find the work function of that metal.

Reveal Answer
A=2πcℏ(η2−λ2/λ1)λ2(η2−1)=1.9eVA=2 \pi c \hbar \frac{\left(\eta^{2}-\lambda_{2} / \lambda_{1}\right)}{\lambda_{2}\left(\eta^{2}-1\right)}=1.9 \mathrm{eV}
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