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invention

Make a Spectrum

by littleBits

Published on April 24, 2014

Explore light waves you can see with a bright LED and a CD.

A spectrum is a range of electromagnetic waves in order of their wavelength. You can always remember the order by thinking of "ROY G BIV". From longest to shortest-Red, Orange, Yellow, Green, Blue, Indigo, Violet. 

As white light bends, each color in the spectrum bends at a slightly different angle because their wavelengths are different sizes. Shorter wavelengths will bend more and longer wavelengths will bend less. 

Why does a CD behave like a prism? They both act as "diffraction grating." The grooves on a CD diffract light into several beams like you saw in this experiment!

You can also find this project on page 15 in the Space Kit booklet.

How To Make It

STEP 1

Make the circuit in the image gallery.

STEP 2

Find a dark place and set the reflective side of the CD opposite a white wall or piece of paper.

STEP 3

Place a bright LED in between the CD and the wall (or paper).

STEP 4

Make a spectrum! How many colors can you find?

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