Question

The X-ray coming from a Coolidge tube has a cutoff wavelength of 80 pm. Find the kinetic energy of the electrons hitting the target.

Answer 1

The kinetic energy of electrons will be - 15.5 KeV.

Given in question is wavelength = 80 pm which will be 8*10^-12 metres.

The energy of X-ray is given by the formula-

E = hc/lambda

H is Plank's constant which has value - 4.14*10^-15 eV/s

C is the speed of light which has value - 3*10^8 m/s.

Keeping values in formula given above-

Energy = 4.14*10^-15*3*10^8/8*10^-12

Energy = 15.5 *10^3 eV

Thus, energy of electrons is - 15.5 KeV.

Answer 2

(a) The energy comes from striking electron’s kinetic energy.

Explanation:

• When a filament is heated, the emission of electrons happens in an x-ray tube.

• The electric field is generated between the target and the filament by a DC battery.

• This makes the electrons strike the target atoms with more speed. This results in the drop of kinetic energy from the electrons and it leads to photon ejection.

• This results in the non-stop x-ray emission.