Dual Nature Of Radiation And Matter Ques 63
63. If the threshold wavelength for a certain metal is $2000 $ $\AA$, then the work-function of the metal is
[1995]
(a) $6.2$ $ J$
(b) $6.2$ $ eV$
(c) $6.2$ $ MeV$
(d) $6.2 $ $keV$
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Answer:
Correct Answer: 63.(b)
Solution:
- (b) Threshold wavelength $(\lambda)=2000 $ $\AA$
$=2000 \times 10^{-10}$ $ m$.
Work function $(W)=\frac{h c}{\lambda}$
$ \begin{aligned} = & \frac{(6.6 \times 10^{34}) \times(3 \times 10^{8})}{2000 \times 10^{-10}} \\ & =9.9 \times 10^{-19} J=\frac{9.9 \times 10^{-19}}{1.6 \times 10^{-19}}=6.2 eV \end{aligned} $
BETA
