## Davisson and Germer experiment
Bearing in mind that the kinetic energy of the electrons is given by ½ mv^{
2} = Ve and that the wavelength associated with them is h/mv,
the wavelength is given by λ = h/√(2Vem).
Substitution of relevant data gives
This wavelength is in the X-ray range. X-rays had already provided information about the spacing of the atomic planes in the nickel crystal, and it is therefore a simple matter to use the Bragg formula (see Bragg's law) to calculate the wavelength of the scattered electrons. As the angle of scattering is 5o°, the angles of incidence and reflection must each be 25°. This implies that the reflecting planes in the crystal are inclined at 25° to the top surface of the crystal. The distance d between the reflecting
crystal planes is d = 215 sin 25° = 90.9 pm. Using the Bragg
formula mλ = 2d sin θ we
get &lambda = 2 × 90.9 sin 65° = 165 pm. Agreement between
the measured and predicted wavelength is therefore established. ## Related category• ATOMIC AND NUCLEAR PHYSICS | |||||||

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