Which characteristic of X-ray spectra does not change when the target material is changed?

The correct answer is option 4) i.e. cutoff wavelength

CONCEPT:

• X-ray spectrum: The X-ray spectrum is defined as the energy distribution of X-ray radiation.
  • X-rays are produced when an electrons incident on the target material inside an X-ray tube emits electromagnetic radiation.
  • There are two types of X-rays produced - characteristic lines and continuous spectrum.
  • Characteristic lines are produced due to the transition of an electron within the atom of the target material.
  • A continuous spectrum is produced due to electrons colliding with the target and decelerating. Therefore, the continuous spectrum has a minimum wavelength.
  • X- rays are emitted when the kinetic energy of the electrons is completely converted into photon energy.

KE of electron = Photon energy

eV = \(\frac{hc}{λ}\)

Where λ is the minimum wavelength.

Minimum wavelength indicates the most energetic photon emitted due to a highly energetic electron, that collides with the target and decelerates to stop immediately after a collision.

EXPLANATION:

• When the target material has changed

1. the intensity of the X-ray spectra varies.
2. The wavelength of characteristic lines varies.
3. The minimum wavelength or the cutoff wavelength remains unchanged.