The work function of sodium metal is

Question:

The work function of sodium metal is $4.41 \times 10^{-19} \mathrm{~J}$. If the photons of wavelength $300 \mathrm{~nm}$ are incident on the metal,

the kinetic energy of the ejected electrons will be

$\left(\mathrm{h}=6.63 \times 10^{-34} \mathrm{Js} ; \mathrm{c}=3 \times 10^{8} \mathrm{~m} / \mathrm{s}\right)$

______$\times 10^{-21} \mathrm{~J}$.

Solution:

$E=W+K \cdot E_{\max }$

$\mathrm{K} \cdot \mathrm{E}_{\max }=\mathrm{E}-\mathrm{W}$

$=\frac{\mathrm{hc}}{\lambda}-4.41 \times 10^{-19}$

$=\frac{6.63 \times 10^{-34} \times 3 \times 10^{8}}{300 \times 10^{-9}}-4.41 \times 10^{-19}$

$=2.22 \times 10^{-19} \mathrm{~J}$

$=222 \times 10^{-21} \mathrm{~J}$

 

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