Question

AN electron beam can undergo diffraction by crystals . through wat potential should beam of electrons be accelerated so that its wavelength becomes equal to 1.54 Armstrong.???

Answer 1

Angstrom, not Armstrong (I made the same mistake at first).
\[1.54Å=1.54*10^{-10}m\]\[E_{(eV)}=eV=hc/\lambda\]
In any case, I get a potential of about 8,051 volts.\[V=hc/e\lambda=(6.63*10^{-34}*3.00*10^8Jm)/(1.60*10^{-19}*1.54*10^{-10}Cm)\]\[V=8.05*10^3J/C=8.05*10^3V\]