It's not hard to calculate wavelength if you know how to use the de Broglie equation.
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This example problem demonstrates how to find the wavelength of a moving electron using de Broglie's equation.
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
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
The wavelength of an electron moving 5.31 x 106 m/sec is 1.37 x 10-10 m or 1.37 Å.