Explanation:

1. Correct. X-rays do have wavelengths in the range of about 1 angstrom (1 A = 10^-10 meters).
2. Correct. X-rays are often generated by bombarding a metal target with high-energy electrons. When the electrons decelerate upon hitting the metal target, X-rays are emitted.
3. InCorrect. Although X-rays have shorter wavelengths, they are not used for radar systems. Radar typically uses radio waves, which have much longer wavelengths.
4. Correct . X-rays are used in radiation therapy to treat certain forms of cancer by targeting and killing cancer cells.