Light Waves

Phenomena that are observed with light show that light has wave properties. Light waves can interfere, diffract and refract as shown by the Michelson interferometer and Young’s experiment.

You can observe the Doppler effect with light. When you look at distant stars that are receding at a great velocity, the wavelength of the light is stretched out by the Doppler effect, shifting it toward the red part of the spectrum. We call the Doppler effect with light either red shift or blue shift, depending on if the stars are receding or approaching.

Other evidence for the wave nature of light includes the phenomenon of polarization. Polarized filters select the portion of light waves that are oscillating in a particular orientation. When two polarized filters are lined up in the same direction, light can be transmitted. When one of the filters is turned by ninety degrees, the light waves no longer pass through.

Many scientists contributed to demonstrating the wave properties of light. Albert Michelson created the Michelson Interferometer to measure interference of light waves. Thomas Young mathematically described a double-slit diffraction pattern. Edwin Hubble used the red shift of stars to calculate the rate at which the universe is expanding. James Clerk Maxwell described the relationship between electricity and magnetism with his famous Maxwell’s Equations, providing an explanation of light being electromagnetic radiation that could travel through a vacuum at the speed of light. Heinrich Hertz conducted early experiments creating and detecting electromagnetic waves that provided a foundation for the development of radio and wireless communication.

Light is described as an electromagnetic wave in which a changing magnetic field generates a changing electric field, which, in turn creates a magnetic field. This combined electric and magnetic field travels without need of a medium.