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Electromagnetic radiation
What is electromagentic radiation?

Electromagnetic radiation is a form of energy that travels in waves. Specifically, electromagnetic energy travels in a transverse wave that oscillates at a certain frequency. The name “electromagnetic” refers to the electric and magnetic field components that constitute the radiative energy. Electromagnetic radiation travels at a particular speed (the speed of light) and its frequency and wavelength are inversely related to one another; as one increases, the other decreases. This relationship is highlighted in the equation below.


Electromagnetic radiation ranges from extremely energetic (gamma rays) to relatively low energy (long radio waves). The equation that relates energy to the frequency of light is given above.

Visible light is a type of electromagnetic radiation. Light, like all electromagnetic radiation, travels in discrete packages called photons. A beam of light is not a single entity, but is rather composed of numerous photons.

The interaction between molecules and electromagenetic radiation are critical for many important processes, including molecular excitation.

Photons: Small packets of light

Photons are the smallest, discrete unit of electromagnetic radiation possible. A photon has an electric field component that is perpendicular to its magnetic field component. These two components are also traveling waves that are always in phase with one another (two waves are in phase when their highest points and lowest points are perfectly aligned) and are always perpendicular to the direction the wave is traveling. The orientation of these waves have a large impact on how they interact with other waves or particles.

Below is a presentation of the photon as a sphere. The orientation of the electric and magnetic fields are represented by differently shaded planes


Try changing the color of light. Notice how the frequency and wavelength of the light changes as you shift the colour. You can drag the photon and electromagnetic fields to explore the model in three dimensions.

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