Why can I see tiny rainbows in drops of water?
Radio waves, microwaves, infrared light, ultraviolet radiation, X-rays, and gamma rays are electromagnetic (EM) radiation, which consists of photons just like visible light. In a vacuum, all types of electromagnetic radiation move at a speed of about 300,000 km/second (the speed of light), but at different wavelengths. When EM radiation goes from air to water, the change will slow down some wavelengths. The shorter the wavelength, the more slowdown. When sunlight hits a drop of water, different wavelengths are slowed down and bent differently to produce a rainbow effect.
Rainbows are produced because blue light is slowed down more in water than red light.