Similar to electron diffraction, neutron diffraction microscope is also used for the determination of the structure of molecules.

From de Broglie's equation,

$\lambda=\frac{\mathrm{h}}{m v}$

$v=\frac{\mathrm{h}}{m \lambda}$

Where,

$v=$ velocity of particle (neutron)

$h=$ Planck's constant

$m=$ mass of particle (neutron)

$\lambda=$ wavelength

Substituting the values in the expression of velocity (v),

$v=\frac{6.626 \times 10^{-34} \mathrm{JS}}{\left(1.67493 \times 10^{-27} \mathrm{~kg}\right)\left(800 \times 10^{-12} \mathrm{~m}\right)}$

$=4.94 \times 10^{2} \mathrm{~ms}^{-1}$

$v=494 \mathrm{~ms}^{-1}$

$\therefore$ Velocity associated with the neutron $=494 \mathrm{~ms}^{-1}$