Question

In an X-ray tube, when electrons, after being accelerated through V volt, strike the target then the wavelength of emitted X-rays is

• A. Not less than $\frac{hc}{eV}$
• B. greater than or equal to $\frac{hc}{eV}$
• C. $\frac{hc}{eV}$
• D. Has all values

Answer 1

The correct option is B greater than or equal to $\frac{hc}{eV}$

Energy of electrons $E=eV$
These electrons strike the plate and the energy is converted into radiation.
The energy of the radiation emitted would lie between 0 and E (depending on how much of the KE of the electron is imparted)

i.e. $\frac{hc}{\lambda }\le eV$ or

$\lambda \ge \frac{hc}{eV}$