What is electromagnetic radiation?

The electromagnetic spectrum is a map of all the types of light that we can identify. It separates all the types of light by wavelength because that directly relates to how energetic the wave is. More energetic waves have shorter wavelengths while less energetic waves have longer wavelengths. Not all light is in the visible spectrum, which is the light you can see. There are many kinds of electromagnetic waves that you can't see. Just look at the spectrum below.

What is a "detector"?

When we talk about a "light detector", we are referring to any instrument that detects electromagnetic radiation. For example, your eye is a type of light detector. It detects white visible light, which contains all the colors of the rainbow from red to violet.

But, remember how we said that some light is "invisible" to the human eye? Well, to detect this type of radiation, we need different detectors to be able to "see" the radiation. X-ray machines, radios, cell phones, and even your television (unless you have cable) are all types of light detectors.

Movies About Light
Do you want to see a cool movie about light? Check this out! light movie (4.9 MB)
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Type of Light Wave Description of Light

Range: 1000 meters to 1 cm

Radio waves are found at the longest wavelengths on the electromagnetic spectrum. These are the lightwaves that are used to send signals to your AM/FM Radio or your television (unless you have cable).

Range: one-tenth of a mm to 1 cm

Microwaves are used in radar and also in your microwave appliance at home that you use for heating food

Infrared Radiation
Infrared radiation is what we like to describe as heat. We can't see infrared waves, but we can feel them. Your body gives off heat, so it is an emitter of infrared radiation.
The range of infrared wavelengths is about sub-millimeters to micrometers (the size of a bacteria).

Want to see a demo you can do with infrared radiation? Click here...

The Visible Spectrum
Visible light is the light that we can see, and thus is the only light detectable by the human eye. White light is visible light, and it contains all the colors of the rainbow, from red to violet.
The range of visible wavelengths is 400 to 700 nanometers.

Ultraviolet light is the radiation from the sun that causes a sunburn when you have been outside too long on a sunny day. But, watch out! You can't see ultra-violet light, so you can still get sunburned on a cloudy day.
The range for ultraviolet light is 10-8 to 10-10 meters.

X-rays are very energetic, and are used in X-ray machines to take pictures of your bones.
The range for X-rays is 10-10 to 10-12 meters.
Gamma rays are the most energetic light waves found on the electromagnetic spectrum. We can find Gamma rays released in nuclear reactions and particle collisions. The range for a gamma ray is in picometers (10-12 meters).
Drawing of Electromagnetic Spectrum courtesy of NASA

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