LEDs (Light Emitting Diodes) come in all colors in the visible, UV and infrared spectrum. They are very inexpensive and also very small and lightweight, yet they produce a relatively intense source of light. A broad spectrum (white) LED, such as this one on a bendable antenna is a very useful item.
Do you have any recommended science experiments using inexpensive materials? Did you find these ones useful? Let us know what you think.