Sky Sensing: Electromagnetic Radiation

Radiation is energy that travels in the form of a particle and/or wave.

Electromagnetic radiation is a kind of radiation. The electromagnetic radiation we can see is light.

Electromagnetic radiation has properties of both particles and waves. The particle form of electromagnetic radiation is a photon. You can think of photons as tiny chunks of energy. Photons have no mass and don’t take up space, and yet we think of them as particles because electromagnetic radiation travels in little bursts, not a smooth uniform wave.

For now, you can think of electromagnetic radiation as a wave. To do this, imagine electromagnetic radiation as a line of energy coming toward you, moving at the speed of light. That wave is oscillating, meaning the line is moving up and down, like this:

How far up and down the line of energy is moving is the amplitude. This is the intensity of the energy—how bright the light is. How far apart the bumps in the line are will give you wavelength. Measuring the wavelength will tell you how often the energy oscillates up and down in a certain amount of time; this will tell you how fast the energy is oscillating, also known as frequency. When talking about electromagnetic radiation people often use the term “wavelength” and “frequency” interchangeably; both refer to how fast the energy is oscillating.

For an electromagnetic wave, the amplitude will tell you the intensity of the light. The frequency will tell you the energy of the light.

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