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MICROWAVES
The radio waves with the shortest wavelengths and the highest frequencies are called microwaves. You may be familiar with the microwaves that cook your food. Microwave ovens work by using microwave about 12 centimeters in length to force water and fat molecules in food to rotate and to heat it up.
Radio waves with longer wavelengths are used in broadcasting. They carry signals for radio and television programs. A broadcast station sends out radio waves at certian frequencies. Your radio or TV atenna picksup the waves and converts it into an electrical signal.
X-rays have much higher energy and much shorter wavelengths than ultraviolet light, and scientists usually refer to x-rays in terms of their energy rather than their wavelength. This is partially because x-rays have very small wavelengths, between 0.03 and 3 nanometers, so small that some x-rays are no bigger than a single atom of many elements.
Radio waves have the longest wavelengths in the electromagnetic spectrum. They range from the length of a football to larger than our planet. They include broadcast waves (for radio and television) and microwaves.
Infrared waves have wavelengths longer than visible and shorter than microwaves, and have frequencies which are lower than visible and higher than microwaves. The infrared waves can be seen with a camera called a thermogram.
Gamma rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. They are produced by the hottest and most energetic objects in the universe, such as neutron stars and pulsars, supernova explosions, and regions around black holes. On Earth, gamma waves are generated by nuclear explosions, lightning, and the less dramatic activity of radioactive decay.
Electromagnetic waves are two important ways that energy is transported in the world around us. You cannot feel, hear, or see most of the waves.
Ultraviolet (UV) light has shorter wavelengths than visible light. Although UV waves are invisible to the human eye, some insects, such as bumblebees, can see them. This is similar to how a dog can hear the sound of a whistle just outside the hearing range of humans.Exposure to UV-B rays increases the risk of DNA and other cellular damage in living organisms. Fortunately, about 95 percent UV-B rays are absorbed by ozone in the Earth's atmosphere. At the right a picture if Earth in UV.
All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light. Cone-shaped cells in our eyes act as receivers tuned to the wavelengths in this narrow band of the spectrum. Visible light that appears white is actually a mixture of many colors. White light from the sun can be separated by a prism into colors of visible spectrum-red, orange, yellow, green, blue, and violet.
The Sun is the dominant source for visible-light waves our eyes receive. The outer-most layer of the Sun's atmosphere, the corona, can be seen in visible light. But it is so faint it cannot not be seen except during a total solar eclipse because the bright photosphere overwhelms it. The photograph at the right was taken during a total eclipse of the Sun where the photosphere and chromosphere are almost completely blocked by the moon. The tapered patterns—coronal streamers—around the Sun are formed by the outward flow of plasma that is shaped by magnetic field lines extending millions of miles into space.