total energy in ground state (t.e) = -13.6ev
hence, n^2 = 13.6/3.4
n=2
v(velocity)= 2pkze^2/nh
hence, v= 2×3.14×9×10^9×1×(1.6× 10^-19)^2 ÷ 2×6.626 ×10^-34
hence,v=10.96×10^5
p(linear momentum)= mv
de broglie wavelength(wl) =h/p
wl= 6.626×10^-34/9.1×10^-31×10.96×10^5
wl=0.06643× 10^-8
wl= 6.643angstorm