Thus, an electromagnetic disturbance moves through the space from one place to another, even if the space is a vacuum. The disturbance acts as if it was a wave, transferring energy from A to B, with a range of wavelengths. The wavelength of the wave depends on how frequently the moving charge is vibrating. A hot molecule vibrates more frequently and therefore produces a wave of smaller wavelength than a colder molecule. However, all electromagnetic waves move at the same velocity in a given medium.
Visible light is the name given to wavelengths to which our eyes are sensitive.