Kinetic energy of electron = 120 × 1.6 × 10–19 J = 1.92 × 10–17 J
(a) Momentum of electron
p = √2Km = √2×1.92×10−17×9.1×10−31 = 5.91 × 10−24kgms−1
(b) Speed of electron
v = √

2K

m

= √

2×1.92×10−17

9.1×10−31

= 6.5 × 106 m s−1
(c) de-Broglie wavelength associated with electron
λ =

h

p

=

6.63×10−34

5.91×10−24

= 1.122

0

A