Waves

•  Radio waves are electromagnetic waves with the longest wavelength and the lowest frequency
• Infrared radiation is emitted from all objects that have thermal heat energy.
• Refraction refers to the change in direction of a wave, as it passes from one medium to another, and is caused by its change in speed.
• Light travels more slowly in a more dense material.
• Refractive index

  The refractive index of a material is a measure of the speed of light as it passes through that material, compared to the speed of light as it passes through a vacuum.