A) 4400\[\overset{0}{\mathop{A}}\,\]
B) 4433 \[\overset{0}{\mathop{A}}\,\]
C) 5434 \[\overset{0}{\mathop{A}}\,\]
D) 433 \[\overset{0}{\mathop{A}}\,\]
Correct Answer: B
Solution :
The work function (W) is the minimum energy needed to remove an electron from a solid to a point immediately outside the solid surface. It is given by \[W=\frac{hc}{\lambda }\] where h is Plancks constant, c the speed of light and\[\lambda \]the threshold wavelength. Given, \[W=2.8\text{ }eV\] \[=2.8\times 1.6\times {{10}^{-19}}J\] \[h=6.6\times {{10}^{-34}}J-s,\] \[c=3\times {{10}^{8}}m/s\] \[\lambda =\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{2.8\times 1.6\times {{10}^{-19}}}\] \[\lambda =4433\times {{10}^{-10}}m\] \[\Rightarrow \] \[\lambda =4433{\AA}\]
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