Wednesday, July 6, 2011

Electromagnetic Spectrum 101:RADIO WAVES :D:D:D

Radio Waves

Radio waves are used not only in radio broadcasting but in wireless telegraphy, telephone transmission, television, radar, navigation systems and telecommunications. Unlike microwaves, radio waves are able to go over obstacles because of their longer wavelengths. radio waves of longer wave lengths are used for AM radio waves while radio waves of shooter wavelengths are used for TV and FM radio.

Dangers:

Large doses of radio waves causes cancer leukemia and other disorders.


By: Teng Zheng Jie, Darryl Lam Wei Cheng and Lionel Lim Yu Xiang
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9 comments:

  1. How do we differentiate the different radio/TV channels?

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  2. Could you tell how the radio wave is being transmitted in the process where two people are having a phone call conversation

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  3. Good examples of the uses of radio waves, but there is only one danger. Definition not clearly explained.

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  4. You said "large doses of radio waves causes cancer leukemia and other disorders" but are there other ways?For example, does being near a source of radio waves cause illnesses?

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  5. Not much in depth , vague but has precise explanation and summarized the basic knowledge of Radio Waves :)

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  6. The advantages can be elaborated further... ☺

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  7. @Lionel Lim - As long as you are at a source of radio waves it cause cancer over extended period of exposure

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  8. This comment has been removed by the author.

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  9. We can differentiate the different radio/TV channel through different radio waves frequency. We are going to look at AM radio, FM (frequency modulated) radio and TV.

    First, let's look at the AM radio band (group of frequencies). AM stands for amplitude modulation. "Modulation" refers to how sound is encoded on a radio wave called a carrier wave; or, more accurately, how the sound affects the carrier wave so that the original sound can later be detected by a radio receiver. AM radio ranges from 535 to 1705kHz (kilohertz, or thousands of cycles per-second of electromagnetic energy). These are the numbers you see on your AM radio dial.

    AM radio waves are of a lower frequency than either FM radio or TV waves, so FM radio and TV waves don't act in the same way as AM radio waves. The FM radio band goes from 88 to 108 MHz (megahertz, or millions of cycles per second). Again, you can see these numbers on your FM radio dial. To keep from interfering with each other FM stations must be 200kHz apart within the same geographic area. However, since the signals of FM stations cover only limited distances, the same frequencies can be used in different areas of the country. Unlike AM radio stations, FM stations, at least in the United States, don't end up being assigned frequencies with nice round numbers like 820 or 1240. Thus, an FM station may be at 88.7 on the dial. You may have noticed that FM stations don't reduce power or sign off the air at sunset. Because of their higher frequency ionospheric refraction doesn't appreciably affect FM or TV signals.
    For the most part, FM and TV signals are line-of-sight. Although this means that FM stations don't interfere with each other, this characteristic creates a couple of other problems.

    First, these waves go in a straight line and don't bend around the earth as AM ground waves do. Thus, they can quickly disappear into space.

    So, the farther away from the FM or TV station you are, the higher you have to have an antenna to receive the FM or TV signal. Note that the earth is round — we hope this doesn't come as a shock to anyone — and, therefore, these signals will literally leave the earth after 50 miles or so.

    And, there's another problem. Since FM and TV signals are line-of-sight, they can be stopped or reflected by things like mountains and buildings. In the case of solid objects like buildings, reflections create ghost images in TV pictures and that "swishing sound" when you listen to FM radio while driving around tall structures, which is why these antennas are very high, tall, and often placed on high places like mountains. AM radio works by changing the amplitude of the carrier wave and FM radio works by changing the frequency of the carrier wave.

    :D

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