Electrons with energy `80 keV` are incident on the tungsten target of an X - rays tube , k- shell electrons of tungsten have `72.5 keV` energy X- rays emitted by the tube contain only

Options

A. a continuous X - rays spectrum (Bremsstrahlung) with a minimum wavelength of `~0.155 A`
B. a continuous X - ray spectrum (Bremsstrahlung) with all wavelengths
C. the characteristic X - ray spectrum of tungsten
D. a continuous X - ray spectrum (Bremsstrahlung) with a minimum wavelength of `~0.155Å` and the characteristic X - ray spectrum of tungsten.

Answer

D

Explanation

Here electron has sufficient energy of knock out the electron from k-shell and hence it will give rise to characteristics spectrum along with the continuous X - ray spectrum .
Photon of minimum possible wavelength is emitted when suppose entire energy of electron goes away as photon .
`80xx10^3xx1.6xx10^(-19) = (hc)/lamda`
`lamda=(hc)/(80xx10^3xx1.6xx10^(-19))`
`lamda=(6.63xx10^(-34)xx3xx10^8)/(80xx10^3xx1.6xx10^(-19))`
`=0.155 xx10^(-10)m`