A wave is a disturbance that travels through a medium or space, transporting energy from one point to another. Waves can travel through a medium, like waves rippling across a lake, or through space, like the electromagnetic waves that carry sunlight to Earth.
- Electromagnetic waves are generally invisible to the human eye, the exception is the visible spectrum, with wavelengths between approximately 400 and 700 nanometres.
- Beyond this range, whether the wavelengths are longer (as in radio and microwaves) or shorter (as in ultraviolet, X-rays, and gamma rays), our eyes cannot detect them.
- Although we cannot see most electromagnetic waves, we can perceive some in other ways. For instance, infrared waves are felt as heat, and electric current (which produces electromagnetic waves) can cause a buzzing sensation in a wire or cause electrocution.