(1) Infrared rays are used to treat muscular strain because these are heat rays. (2) Radio waves are used for broadcasting because these waves have very long wavelength ranging from few centimeters to few hundred kilometers. (3) X-rays are used to detect fracture of bones because they have high penetrating power but they can't penetrate through denser medium like dones. (4) Ultraviolet rays are absorbed by ozone of the atmosphere.