Question

A beam of monoenergetic electrons, which have been accelerated from rest by a potential U, is used to form an interference pattern in a Young’s Double Slit experiment. The electrons are now accelerated by potential 4 U. Then the fringe width

• A. remains the same
• B. is half the original fringe width
• C. is twice the original fringe width
• D. is one-fourth the original fringe width

Answer 1

The correct option is B is half the original fringe width

$eV=\frac{1}{2}m{v}^{2}so,eV=\frac{{\rho }^2}{2m}and\lambda =\frac{h}{\rho },\Rightarrow V\alpha \frac{1}{{\lambda }^2}and\beta =\frac{n\lambda D}{d}$
So as potential U becomes 4 U then $\beta$ becomes half