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ch 22 concepts
5
Physics
04/01/2013

Term
 Consider the following: radio waves emitted by a weather radar system to detect raindrops and ice crystals in the atmosphere to study weather patterns; microwaves used in communication satellite transmissions; infrared waves that are perceived as heat when you turn on a burner on an electric stove; the multicolor light in a rainbow; the ultraviolet solar radiation that reaches the surface of the earth and causes unprotected skin to burn; and X rays used in medicine for diagnostic imaging.
Definition
 be prepared to review these concepts
Term

Which of the following statements correctly describe the various forms of EM radiation listed above?

Check all that apply.

 They have different wavelengths. They have different frequencies. They propagate at different speeds through a vacuum depending on their frequency. They propagate at different speeds through nonvacuum media depending on both their frequency and the material in which they travel. They require different media to propagate.
Definition
 These are correct: 1,2,4 They have different wavelengths They have different frequencies. They propagate at different speeds through nonvacuum media depending on both their frequency and the material in which they travel why the others are wrong: Recall that for any EM wave of frequency [image] and wavelength [image] there exists a relation [image], where [image] is the wave speed. All EM waves that travel through a vacuum have the same speed as light: [image].
Term
 The frequency and wavelength of EM waves can vary over a wide range of values. Scientists refer to the full range of frequencies that EM radiation can have as the electromagnetic spectrum. Electromagnetic waves are used extensively in modern technology. Many devices are built to emit and/or receive EM waves at a very specific frequency, or within a narrow band of frequencies. Here are some examples followed by their frequencies of operation: garage door openers: 40.0 [image], standard cordless phones: 40.0 to 50.0 [image], baby monitors: 49.0 [image], FM radio stations: 88.0 to 108 [image], cell phones: 800 to 900 [image], Global Positioning System: 1227 to 1575 [image], microwave ovens: 2450 [image], wireless Internet technology: 2.4 to 2.6 [image].
Definition
Term

Which of the following statements correctly describe the various applications listed above?

Check all that apply.

 1.All these technologies use radio waves, including low-frequency microwaves. 2.All these technologies use radio waves, including high-frequency microwaves. 3.All these technologies use a combination of infrared waves and high-frequency microwaves. 4.Microwave ovens emit in the same frequency band as some wireless Internet devices. 5.The radiation emitted by wireless Internet devices has the shortest wavelength of all the technologies listed above. 6.All these technologies emit waves with a wavelength in the range 0.10 to 10.0 m 7.All the technologies emit waves with a wavelength in the range 0.01 to 10.0 km

Definition
 statement 1, 4, 5,6 All these technologies use radio waves, including low-frequency microwaves. Microwave ovens emit in the same frequency band as some wireless Internet devices. All these technologies emit waves with a wavelength in the range 0.10 to 10.0 m The radiation emitted by wireless Internet devices has the shortest wavelength of all the technologies listed above.
Term

Based on this information, which of the following statements is correct?

Check all that apply.

 The earth absorbs visible light and emits radiation with a shorter wavelength. The earth absorbs visible light and emits radiation with a longer wavelength. The earth absorbs visible light and emits radiation with a lower frequency. The earth absorbs visible light and emits radiation with a higher frequency.
Definition
 The earth absorbs visible light and emits radiation with a longer wavelength. The earth absorbs visible light and emits radiation with a lower frequency. aka choice 2 & 3 recall: Recall that the wavelength of a wave is inversely proportional to its frequency. Even though our atmosphere absorbs a very small amount of visible light, it strongly reflects and absorbs infrared waves. Therefore the radiation emitted by the earth does not leave the atmosphere. Instead, it is reflected back into it, contributing to a warming effect known as the greenhouse effect.
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