State the de-Broglie principle and explain it.

(N/A) de-Broglie principle: The French physicist,de-Broglie,in $1924$ proposed that matter,like radiation,should also exhibit dual behaviour,i.e.,both particle and wavelike properties. This means that just as the photon has momentum as well as wavelength,electrons should also have momentum as well as wavelength.
Mathematical relation: The following relation exists between wavelength $(\lambda)$ and momentum $(p)$ of a material particle:
$\lambda = \frac{h}{m v} = \frac{h}{p} \quad$ (Eq. $- 2.30$)
Proof of de-Broglie's dual behaviour: de-Broglie's prediction was confirmed experimentally when it was found that an electron beam undergoes diffraction,a phenomenon characteristic of waves.
Limitation: According to de Broglie,every object in motion has a wave character. The wavelengths associated with ordinary objects are so short (because of their large masses) that their wave properties cannot be detected.
The wavelengths associated with electrons and other subatomic particles (with very small mass) can,however,be detected experimentally.