Solution :
According to be Brogile equation $\lambda= \large\frac{h}{mv}$
Mass of electron $=9.1 \times 10^{-31}\;kg$
Planck's constant $=6.626 \times 10^{-34}\;kgm^2s^{-1}$
Velocity of electron =1 % of speed of light
$\qquad= 3.0 \times 10^8 \times 0.01=3 \times 10^{6}\;ms^{-1}$
wave length of electron $(\lambda)= \large\frac{h}{m}$
$\qquad= \large\frac{(6.626 \times 10^{-34}\;kg m^2s^{-1})}{(9.1 \times 10^{-31}\;kg) \times (3 \times 10^6 ms^{-1})}$
$\qquad= 2.43 \times 10^{-10}\;m$