Question

An electron microscope works on principle of diffraction of electron beam .In the electron microscope if the Potential is increased from 20 kV to 80 kV, the resolving power R of the microscope will become

• A. R
• B. 2R
• C. 4R
• D. $\frac{R}{2}$

Answer 1

The correct option is B 2R

$\lambda =\frac{h}{\sqrt{2mqV}}$
$\lambda \propto \frac{1}{\sqrt{V}}$
Resolving power, $R\propto \frac{1}{\lambda }\Rightarrow R\propto \sqrt{V}$
Resolving power becomes 2 times.