Question

A beam of electrons is used in a YDSE experiment to slit width is $d$, when the velocity of electrons is increased, then

• A. no interference is observed
• B. fringe width increases
• C. fringe width decreases
• D. fringe width remains same

Answer 1

Answer: (C)

When velocity of an electron increases, the moments of electron $(p=mv)$ increases. The de-Broglie wavelengths $(\lambda =h/mv)$ decreases. The fringe width is, $\beta =\lambda D/d$, so $\beta \propto \lambda$. Hence, if $\lambda$ decreases then $\beta$ decreases.