Perhaps the simplest optical instrument is the lens magnifier. Without optical aid, we cannot see things close up. The eye will simply not focus closer than about 0.25 m (unless you are nearsighted)
A spectroscope is a device that lets us find out what things are made of. It works by taking light and splitting it up into its component colors. Different elements make different colors when they glow.
In this section we will build a toy called the Polariscope. As you can see from the above photograph, the Polariscope creates patterns of beautiful colors, somewhat like a kaleidoscope, but by an entirely different mechanism.
In this section we will show you how to make a powerful solar concentrator that can cook four or five hotdogs in minutes.
At either end of the rainbow there is light we can not see. Below the red end is near infrared light, shorter in wavelength than the infrared we feel as heat. Above the violet end of the rainbow is near ultraviolet, longer in wavelength than the ultraviolet light that causes sunburn.
In this section we will describe how to make a marshmallow roaster, powered by the sun. It can be made from readily available materials, and while it is probably a little safer than the traditional method of roasting marshmallows (over a campfire), it can still start fires, and should be used only by those you would trust with a box of matches.
You have probably seen the beautiful rainbow colors caused by a tiny bit of oil floating in a puddle of water. In this project, we are going to capture those colorful patterns on paper, in a permanent form, so you can view them anytime you like, without a messy puddle.
Make sure the transistor radio is turned off, and the laser is on. Plug the earphone jack of the laser into the earphone socket of the radio.
How would you like to talk over a laser beam? In about 15 minutes you can set up your own laser communication system, using cheap laser pen pointers and a few parts from Radio Shack.
By using a pair of polarizing filters and a property of certain materials called birefringence we can photograph the hidden stresses in hard plastics.