1. Tardigrade
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  4. Light of wavelength 4000 mathringA falls on a photosensitive metal and a negative 2 V potential stops the emitted electrons. The work function of the material (in eV ) is approximately (h=6.6 × 10-34 Js , e=1.6 × 10-19 C. . c=3 × 108 ms -1)

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Q. Light of wavelength $4000\, \mathring{A}$ falls on a photosensitive metal and a negative $2\, V$ potential stops the emitted electrons. The work function of the material (in $eV$ ) is approximately $\left(h=6.6 \times 10^{-34} Js ,\, e=1.6 \times 10^{-19} C\right.$ $\left. c=3 \times 10^{8} ms ^{-1}\right)$

Dual Nature of Radiation and Matter

Solution:

Energy of incident light $E( eV )=\frac{12375}{4000}=3.09\, eV$
Stopping potential is $-2 V$ so $K_{\max }=2\, eV$
Hence by using $E=W_{0}+K_{\max }$
$\Rightarrow W_{0}=1.09\, eV \approx 1.1\, eV$