De Broglie Wavelength Example Problem

Finding the Wavelength of a Moving Particle

It's not hard to calculate wavelength if you know how to use the de Broglie equation.
It's not hard to calculate wavelength if you know how to use the de Broglie equation. Justin Lewis, Getty Images

This example problem demonstrates how to find the wavelength of a moving electron using de Broglie's equation.​

Problem:

What is the wavelength of an electron moving at 5.31 x 106 m/sec?

Given: mass of electron = 9.11 x 10-31 kg
h = 6.626 x 10-34 J·s

Solution:

de Broglie's equation is

λ = h/mv

λ = 6.626 x 10-34 J·s/ 9.11 x 10-31 kg x 5.31 x 106 m/sec
λ = 6.626 x 10-34 J·s/4.84 x 10-24 kg·m/sec
λ = 1.37 x 10-10 m
λ = 1.37 Å

Answer:

The wavelength of an electron moving 5.31 x 106 m/sec is 1.37 x 10-10 m or 1.37 Å.