Answer

We have the wavelength - from this we can find the momentum by using the DeBroglie equation

 

λdB= h/p

so p = h/l

= 6.63 x 10-34/1.2 x 10-10

= 5.5 x 10-24 Ns

 

and p = root of (2meV)

so p2/(2me) = V

= (5.5 x 10-24 )2 / (2 x 9.1 x 10-31 x 1.6 x 10-19)

= 105 V Ans