Given the mass of an electron is 9.1 � 10�31 kg and k.e. is 3.0 � 10�25 j, calculate its wavelength.

Mass = 9.1 × 10^31

KE = 3.0 × 10^–25 J

h = 6.6×10 -34 Js ie Planck’s constant

Wavelength =h/mv = h/p p=momentum

p=√2Em

so Wavelength= h/√2Em

= 6.6 x 10-34/√2 x 3.0 x 10-25 x 9.1 x 10 -31

= 6.6 x 10 -34/√54.6 x 10 – 56

= 6.6 x 10 -34/ 7.4 x 10 – 28

= 8.99 x 10 -7 m