The electromagnetic spectrum shows the different energies of light and how the energy relates to different frequencies. The wavelength (λ) equals the speed of light (c) divided by the frequency (ν), or λ = c / ν. The speed of light is: c = 3 x 10⁸ m/s (300,000,000 meters per second).

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You and I don’t detect most electromagnetic waves. Our eyeballs can only ‘see’ in the 400-700 nm (nanometer) range, which is only a small part of the entire spectrum, so we need special detectors to find the rest of the photons zipping around.

Radio signals are picked up using an antenna (similar to your satellite dish in the backyard). These waves have the longest wavelengths and lowest energy in the electromagnetic spectrum.

Making IR Visible to the Human Eye

Infra-red light is in the part of the electromagnetic spectrum that isn’t usually visible to human eyes, but using this nifty trick, you will easily be able to see the IR signal from your TV remote, remote-controller for an RC car, and more!

Exercises

1. Look over your data table. What kinds of objects (plastic, metal, natural, etc.) allow infrared light to pass through them?
2.  Why does the camera work in making the infrared light visible?

X-rays are more difficult to detect, because they would rather go through the detector than bounce off of it, so we use complicated mathematics and the shadows of the photons to “see” x-rays.

Gamma rays are the toughest to detect – they are very highly energized packets of light that would rather zoom through mirrors than be detected. Gamma radiation has the highest energy and highest frequency in the electromagnetic spectrum.

Click here to go to next lesson on Visible Light

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