Question

Question 2.20 Calculate the wavelength of an electron moving with a velocity of 2.05 × 107 ms–1.

Class XI Structure of Atom Page 66

Answer 1

V= 2.05 x107 (given)
By de Broglie’s equation,



 λ = wavelength of moving particle

m = mass of particle (9.10939 x 10-31)

v = velocity of particle

h = Planck’s constant (6.62 x 10-34)

Substituting the values in the expression of λ:

in the file.............

Hence, the wavelength of the electron moving with a velocity of 2.05 × 107 ms–1 is 3.548 × 10–11 m.

Answer 2

we know,
mass of electron ( m ) = 9.1 × 10^-31 Kg
Plank's constant ( h ) = 6.626 × 10^-34 Js
velocity of electron ( v ) = 2.05 × 10^7 m/s

according to De - broglie's wavelength,
λ = h/mv
= 6.626 × 10^-34 Js /s/9.1 × 10^-31 Kg × 2.05 × 10^7 m/s
= 0.35 × 10^-10 m
= 0.35 A°

hence, wavelength of electron = 0.35 A° or, 3.5 × 10^-11 m