There are so many different types of LEDs on the market (even of the same size and color), how do you tell the difference between them and which one you should use for your particular application? The simple tests descibed here compare...

Learn about additive mixtures in this activity. Understand how your rods and cones work together to see color.

In this full-color image, a neuron is expressing the light-gated cation channel channelrhodopsin-2 (small green shapes), and is being illuminated by a focused beam of blue light (coming from the top).

Explains where visible light fits into the electromagnetic spectrum and the wavelengths for the different colors we see.