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Transcript
Electromagnetic wave Names: Ahmed Ali Saeed Al Sharhan Khalid alneaimi Grade 12-3 6.1 Describe electromagnetic waves : 6.1.1 III. Making Electromagnetic Waves: • Recall: EM waves are made by a vibrating charge. • This means that a vibrating charge has both an electric. • field and a magnetic field. • As the charge vibrates, the electric and magnetic fields change. • A vibrating electric charge creates an EM wave that travels outward in all directions from the charge. • EM waves are transverse waves because the electric and magnetic fields vibrate at right angles to the direction the wave travels. ELECTROMAGNETIC ENERGY • When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist. • Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. 6.1.2 • Radiant energy is the energy of electromagnetic waves. • The quantity of radiant energy may be calculated by Integrating radiant flux (or power) with respect to time and, like all forms of energy. • The term is used particularly when radiation is emitted by a source into the surrounding environment. • Radiant energy may be visible or invisible to the human eye. INFRARED WAVES • A remote control uses light waves just beyond the visible spectrum of light— infrared light waves—to change channels on your TV. • A typical television remote control uses infrared energy at a wavelength around 940 nanometers. INFRARED FILM • Color Infrared film can record near-infrared energy and can help scientists study plant diseases where there is a change in coloring and cell structure. • These two images show the difference between a color infrared photo and a natural color photo of trees and baby in a park. 6.2 Describe electromagnetic spectrum : 6.2.1 { Radio waves, television waves, and microwaves are all types of electromagnetic waves. They differ from each other in wavelength. Wavelength is the distance between one wave crest to the next }. 6.2.2 {The following electromagnetic waves to their frequencies } : • • • • • • • Gamma rays: 1019 Hz & Higher X-rays: 1016 to 1019 Hz Ultraviolet waves: 1014 to 1016 Hz Light waves: 7.85 to 4.85 X 1014 Hz Infra red waves: 1 x 1012 to 4.3 X 1014 Hz Microwaves: 3 X 108 to 3 x 1011 Hz Radio waves: 3 X 104 to 3 X 108 Hz 6.2.3 • The last line of numbers in power of 10 gives the wavelength in m. The regions sometimes do not have a clear cut, because there is considerable overlap. For example, radio waves and microwaves boundary is very vague, but public regulation for their application (usage) is strict. 6.3 Describe radio communications : 6.3.1 • Some radio waves carry an audio signal from a radio station to a radio. • These radio waves carry information that a radio uses to create sound. • You hear a sound wave when the compressions and rarefactions the sound wave produces reach your ears. • A radio wave does not needed wires as it travels through air. 6.3.2 • Radio waves are electromagnetic waves. • Electromagnetic waves include waves such as X rays, ultraviolet light, visible light, infrared rays. • Radio waves, including AM radio band, FM radio band, and TV, which uses AM for the picture and FM for the sound.