The work function of a photosensitive material is $4.0 \mathrm{eV}$. The longest wavelength of light that can cause photon emission from the substance is (approximately) (1) $310 \mathrm{~nm}$ (2) $3100 \mathrm{~nm}$ (3) $966 \mathrm{~nm}$ (4) $31 \mathrm{~nm}$ - Noon Academy

The work function of a photosensitive material is $4.0 \mathrm{eV}$ . The longest wavelength of light that can cause photon emission from the substance is (approximately) (1) $310 \mathrm{~nm}$ (2) $3100 \mathrm{~nm}$ (3) $966 \mathrm{~nm}$ (4) $31 \mathrm{~nm}$

Physics | Physics

The work function of a photosensitive material is $4.0 \mathrm{eV}$ . The longest wavelength of light that can cause photon emission from the substance is (approximately) (1) $310 \mathrm{~nm}$ (2) $3100 \mathrm{~nm}$ (3) $966 \mathrm{~nm}$ (4) $31 \mathrm{~nm}$

Answer (1)
Sol. As $E=\frac{12400}{\lambda}(E$ is in $\mathrm{eV}$ and $\lambda$ is in $\AA$ )
$\begin{array}{l} \lambda=\frac{12400}{4} \\ =3100 \mathrm{~A} \\ \therefore \quad \lambda=310 \mathrm{~nm} \end{array}$

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