Science Projects: How Do Light Waves Travel?

A prism can be used to separate white light.

By definition, light is a type of electromagnetic radiation that travels in waves. Visible light is the portion of electromagnetic radiation that can be seen by the human eye. Several types of electromagnetic radiation occur outside the visible spectrum, including ultraviolet and infrared light. Several science projects can be set up to explore the wave properties of light.

Separating Light Waves

There are several experiments that can divide white light into its component colors. Two prisms, a mirror, a sheet of white poster board, and a source of white light, such as sunlight, will allow you to separate the white light into its component colors as it passes through a prism. Using the mirror to pass the separated light through the second prism will allow the separated light colors to return to the original white light. Placing the white poster board between the two prisms will show the individual colors more clearly.

Bending Light

Fill a clear glass with water, then place a pencil in the glass so that part of the pencil is sticking out. Look at the pencil from the side, and you should notice that the part of the pencil above the water no longer lines up with the portion in the water. If you try this experiment using a clear plastic glass, you will probably notice that the two portions of the pencil now line up. Light travels more slowly through glass than plastic, which accounts for the unmatched pencil parts. Try this experiment using different liquids, such as syrup, vegetable oil, club soda and vinegar.

Capturing a Sunset

"Red sky in the morning, sailors take warning; Red sky at night, sailors delight" goes the old saying. This weather prediction is based on the water and dust particles in the air. You can try to duplicate this look in the sky by filling two-thirds of a beaker or glass jar with water. Next add a teaspoon of milk to the water and stir. Take this glass and a flashlight into a dark room. Now shine the flashlight into the glass at different angles and notice how the color changes due to the suspended particles of milk in the water. These milk particles will act much like dust particles in the atmosphere. Look at the glass from the side with the flashlight shining down on the water from the top and you should see a bluish tint. Holding the flashlight to the side and looking through the water toward the flashlight from the opposite side of the glass should produce a red tint. This experiment duplicates the way the dust particles in the atmosphere scatter sunlight; the more particles the light penetrates, the redder the tint.

Taking Photos

Create a pinhole camera from a shoe box by using a nail or needle to punch a hole in one of its short sides. Cut a piece of waxed paper that's as tall as the box, but a few inches longer than the short end, so you have room to fasten it to the long sides of the box. Tape the waxed paper in the box about four to six inches from the hole to make a screen. Tape the lid on the box, so that no light can enter, and so that the lid can not be accidentally opened. Now cut out the end of the box opposite the hole. You may want to curve the edges so it will fit over your face. Go outside, place the box over your face, then look at a brightly lit object. You should see the image appear on your wax paper screen. Note that the image is upside down and reversed. Since light can only travel in a straight line, light reflecting from the top of an object will travel down through the hole and onto the screen while those rays reflecting from the bottom of an object will travel upward. The light reflected from each side will travel to the opposite sides for the same reason.

References

• Science Made Simple: Why s the Sky Blue?
• Science Buddies: Point, Click, Shoot! Photography with a Pinhole Camera
• Exploratorium: To Do and Notice--Making a Pinhole Viewer