Duane–Hunt law

pm

.

The Duane–Hunt law, named after the American physicists

V into a metal target.

The maximum frequency ν_max is given by[2]

${\displaystyle \nu _{\rm {max}}={\frac {eV}{h}},}$

which corresponds to a minimum wavelength

${\displaystyle \lambda _{\rm {min}}={\frac {hc}{eV}},}$

where h is

. This can also be written as:

${\displaystyle \lambda _{\rm {min}}\approx {\frac {1239.8{\text{ V.pm}}}{V{\text{ in kV}}}}.}$

The process of X-ray emission by incoming electrons is also known as the inverse photoelectric effect.

Explanation

In an

associated with the atoms in the target.

The spectrum has a sharp cutoff at low wavelength (high frequency), which is due to the limited energy of the incoming electrons. For example, if each electron in the tube is accelerated through 60 

: There is no X-ray of any kind beyond the cutoff. However, the cutoff is most obvious for the continuous spectrum.

The exact formula for the cutoff comes from setting equal the kinetic energy of the electron, E = eV, and the energy of the X-ray photon, E = hν = hc/λ.

References