H.S. Level - Sound and Light Waves

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Sounds are produced by the vibrations of material objects, and travel as a result of

momentum transfer when air molecules collide. Our ‘subjective impression' about the frequency of a sound is called pitch. High pitch has high vibration frequency, while low pitch has a low vibration frequency. A pure musical tone consists of a single pitch or frequency. However, most musical tones are "complex summations" of various pure frequencies - one characteristic frequency, called the fundamental, and a series of overtones or harmonics Younger people can usually hear pitches with frequencies from about 20 hertz (infrasonic) to 20,000 (ultrasonic) hertz. We can't hear above 20,000 hertz or below 20 hertz (ultra and infrasonic waves).

Light is both part particle and part wave. Light is "the electromagnetic radiation that may be perceived by the human eye". It consists of photons, which are massless bundles of concentrated electromagnetic energy. Light's lower frequency is red, and the higher frequency is blue. Like sound, light has frequencies humans can't detect. Ultraviolet light is at a frequency higher than violet, and infrared is at the frequency lower than the red of visible light. We get UV (ultraviolet) rays from the sun, and infrared is used in night vision to see better.

Sound travels at about 1,200 k/hr while light travels at about 300,000 km/s. It's easy to notice how slowly sound travels. Take, for instance, a soccer field. If you were standing at one end and you see somebody kick the ball, it will probably take a second for you to hear the person kick it. You hear the sound a few seconds after you see the ball moving. The farther you are away, the longer the space is between you seeing the ball being kicked and you actually hearing it. Light can travel around the earth 7 and a half times in one second.

Light and sound are similar in some ways too, though. They both have frequencies that humans cannot detect (ultraviolet, infrasonic, etc.)....
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