Dual Nature of Radiation and Matter - Result Question 62
66. If the threshold wavelength for a certain metal is $2000 \AA$, then the work-function of the metal is
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======= ####66. If the threshold wavelength for a certain metal is $2000 \AA$, then the work-function of the metal is
c3eec34ec6b1fad69db54a20ad4b2dca40c2aa54 (a) $6.2 J$
(b) $6.2 eV$
(c) $6.2 MeV$
(d) $6.2 keV$
[1995]
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Answer:
Correct Answer: 66. (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} $
