Answer
0.29 nm
Work Step by Step
λ = $\frac{h}{mv}$
h = $6.626\times10^{-34}Js$
m = $9.11\times10^{-31}kg$
v = $2.5\times10^{8} cm/s$ = $2.5\times10^{6}ms^{-1}$
λ = $\frac{6.626\times10^{-34}Js}{9.11\times10^{-31}kg\times2.5\times10^{6}ms^{-1}}$ = $2.9\times10^{-10}$ = 0.29 nm
