Answer
$2.9\times 10^6\frac{m}{s}$
Work Step by Step
We know that
$v_e=\frac{h}{m_e\lambda}$
We plug in the known values to obtain:
$v_e=\frac{6.63\times 10^{-34}J.s}{(9.11\times 10^{-31}Kg)(0.25\times 10^{-9}m)}$
$v_e=2.9\times 10^6m/s$
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