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Q.
A beam of electrons is used in a YDSE experiment to slit width is $d$, when the velocity of electrons is increased, then
Ray Optics and Optical Instruments
Solution:
When velocity of an electron increases, the moments of electron $(p=m v)$ increases. The de-Broglie wavelengths $(\lambda=h / m v)$ decreases. The fringe width is, $\beta=\lambda D / d$, so $\beta \propto \lambda$. Hence, if $\lambda$ decreases then $\beta$ decreases.