Question

Where does the energy of a photon of characteristic X-rays from a Coolidge tube comes from?

• A. The Kinetic Energy of the striking electron
• B. The Kinetic Energy of the free electrons of the target
• C. The Kinetic Energy of the ions of the target
• D. An atomic transition in the target

Answer 1

The correct option is D An atomic transition in the target

Characteristic $X$-rays are emitted from heavy elements when their electrons make transitions between the lower atomic energy levels. The characteristic $X$-rays emission occur when vacancies are produced in the $n=1$ or K-shell of the atom and electrons drop down from above to fill the gap. The $X$-rays produced by transitions from the $n=2$ to $n=1$ levels are called K-alpha $X$-rays, and those for the $n=3$ to $n=1$ transition are called K-beta $X-$rays.