The wavelength
of 20 eV electrons is about 2.7 Angstroms (2.7 x 10-10
m)
Rationale
It is best to simplify the equation by substituting for all the known variables except the electron voltage, V , and simultaneously multiplying by 1010 to accommodate the change in units from metres to Angstroms : this gives
Wavelength, λ ~ ( 150 / V )1/2 Angstroms
Substituting V = 20 gives a wavelength of around 2.7 Angstroms .