Vibrations travel through the air in waves to reach a listener's ears.
Sound is a kind of energy. It is made when vibrations cause movement in air particles. The particles bump into each other, vibrate and cause sound waves. The waves then travel to the ear, where they become sound. Light is also a kind of energy. Like sound, it can be a wave. However, light can also behave like a particle. Both sound and light have unique properties. Some basic experiments can help young students to understand these two forms of energy.
See Sound
A few grains of rice and some common kitchen materials demonstrate that sound makes the air vibrate.
Tightly stretch a piece of heavy plastic over the top of an empty plastic bowl. Secure the plastic with a rubber band, and then tape it to the side of the bowl. Sprinkle a few grains of rice on top of the plastic. Hold a heavy saucepan next to the bowl and bang the bottom of the pan with a wooden spoon. Sound waves from the pan will travel through the air and make the plastic vibrate. The vibrating plastic will make the rice hop.
String Telephones
Cardboard tubes can be made into a variation of the old familiar tin can telephone.
Cover one end of two different cardboard tubes with tracing paper. Tape the paper tightly to the tubes. Poke a small hole in the center of the paper on each tube. Thread one end of a five-foot string through the hole in one tube and the other end through the other tube. Tie paper clips to the strings to keep them from sliding out. With a tight string, talk into one tube while a friend listens with the other tube held to his ear. Sound waves will travel through the paper and along the string to create a primitive telephone.
Bending Light
Refraction can be observed when watching objects in water.
Put a coin in the center of an opaque bowl and secure it with small piece of modeling clay. Move backward away from the bowl until the coin is not visible. Without moving, have a partner slowly pour water into the bowl. Stop when the coin becomes visible. This experiment demonstrates refraction, or the bending of light. When the bowl is empty the coin is not visible because it is blocked by the edge of the bowl. When the bowl has water in it, the light bends over the edge, allowing the coin to become visible.
Make a Rainbow
Rainbows occur when water droplets break light into its separate colors.
When light travels in a straight line it seems to be colorless, but it is really comprised of seven different colors. This can be seen when light passes through rain and makes a rainbow. Break light into its colors by placing a mirror in a glass at an angle. Turn the glass so the mirror is facing the sun. Hold a piece of white paper at a slant in front of the glass. Move it around slowly until a rainbow of colors appears. These colors are the wavelengths of light that are being broken apart.
