A certain metallic surface is illuminated by monochromatic radiation of wavelength $\lambda$. The stopping potential for photoelectric current for this radiation is 3V0. If the same surface is illuminated with a radiation of wavelength 2$\lambda$, the stopping potential is V0. The threshold wavelength of this surface for photoelectric effect is ____________ $\lambda$.
Answer (integer)
4
Solution
$KE = {{hc} \over \lambda } - \phi hc$<br><br>$e(3{V_0}) = {{hc} \over \lambda } - \phi$ ..... (i)<br><br>$e{V_0} = {{hc} \over {2\lambda }} - \phi$ ..... (ii)<br><br>Using (i) & (ii)<br><br>$\phi = {{hc} \over {4{\lambda _0}}} = {{hc} \over {{\lambda _t}}}$<br><br>${\lambda _t} = 4{\lambda _0}$
About this question
Subject: Physics · Chapter: Dual Nature of Matter and Radiation · Topic: Photoelectric Effect
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