Science_Lab_Yellow / Lesson 6: Wavelengths Longer Than Red Light
Wavelengths Longer Than Red Light
What will we be learning today?
Which Wavelengths Are Longer than Red Light?
The wavelengths of light listed here are longer than red. They are invisible but have important properties and uses. Radio Waves
Radio waves are the longest waves of the electromagnetic spectrum. You do not see them-and you do not hear them. Broadcast stations use them to carry signals in a kind of code-AM or FM. In AM the height of the waves is changed to carry the signal. In FM the frequency changes. The number of your favorite radio station represents the frequency at which the station sends out radio waves. When these signals are picked up by a radio or television, they produce the sounds and sights that you hear and see. Radar
Some animals, such as bats and whales, send out sound waves with a high frequency. The echo of the waves helps the animals locate things. Radar works in a similar way. Radar stands for " radio detecting and ranging." Radar uses radio waves that reflect off many objects. The waves can help weather forecasters detect rain and thick fog. Microwaves
A microwave oven uses electromagnetic waves, too. Microwaves are shortwave radio waves. Water in foods absorbs microwaves very readily. The energy from the absorbed microwaves speeds up the water molecules inside the food. As the water molecules move faster, the food gets hotter. Microwave ovens can heat many foods faster, using less energy than a regular oven. Infrared Light
Infrared means "just beyond red." Infrared waves are next to visible red waves in the spectrum. When you stand in sunlight, it is the Sun's infrared waves that warm you. All objects give off infrared waves, depending on their temperature. Warmer objects give off more infrared waves than cooler objects do. Special photographic film and electronic sensors can detect infrared light.
This photograph was taken with film that picks up infrared light.