What are X-rays? How are they produced? Give two uses of X-rays.

The waves of the electromagnetic spectrum whose wavelength lies between $\displaystyle 1$ nm and $\displaystyle 10^{-3} \mathrm{~nm}$.

X-rays are produced by X-ray tubes, or when inner-shell electrons move from one energy level to a lower energy level.  (Alternatively: waves produced when a metal target is bombarded by high energy electrons.)

Used as a diagnostic tool in medicine.

For treatment of certain forms of cancer.

Scanning luggage at airports.

Inspecting materials for structural flaws.