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What property of light corresponds to loudness in sound?

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Is the visible region a major portion of the electromagnetic spectrum?

No, it is very narrow and just a small portion of the overall electromagnetic spectrum.

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Can the human body detect electromagnetic radiation that is outside the visible region of the spectrum?

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Radio waves normally have their E and B fields in specific directions, whereas visible light usually has its E and B fields in random and rapidly changing directions that are perpendicular to each other and to the propagation direction. Can you explain why?

Visible light is typically produced by changes of energies of electrons in randomly oriented atoms and molecules. Radio waves are typically emitted by an ac current flowing along a wire, that has fixed orientation and produces electric fields pointed in particular directions.

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Give an example of resonance in the reception of electromagnetic waves.

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Illustrate that the size of details of an object that can be detected with electromagnetic waves is related to their wavelength, by comparing details observable with two different types (for example, radar and visible light).

Radar can observe objects the size of an airplane and uses radio waves of about 0.5 cm in wavelength. Visible light can be used to view single biological cells and has wavelengths of about 10 −7 m .

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In which part of the electromagnetic spectrum are each of these waves:
(a) f = 10.0 kHz, (b) f = λ = 750 nm ,
(c) f = 1.25 × 10 8 Hz , (d) 0.30 nm

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In what range of electromagnetic radiation are the electromagnetic waves emitted by power lines in a country that uses 50-Hz ac current?

ELF radio waves

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If a microwave oven could be modified to merely tune the waves generated to be in the infrared range instead of using microwaves, how would this affect the uneven heating of the oven?

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A leaky microwave oven in a home can sometimes cause interference with the homeowner’s WiFi system. Why?

The frequency of 2.45 GHz of a microwave oven is close to the specific frequencies in the 2.4 GHz band used for WiFi.

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When a television news anchor in a studio speaks to a reporter in a distant country, there is sometimes a noticeable lag between when the anchor speaks in the studio and when the remote reporter hears it and replies. Explain what causes this delay.

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Problems

How many helium atoms, each with a radius of about 31 pm, must be placed end to end to have a length equal to one wavelength of 470 nm blue light?

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If you wish to detect details of the size of atoms (about 0.2 nm) with electromagnetic radiation, it must have a wavelength of about this size. (a) What is its frequency? (b) What type of electromagnetic radiation might this be?

a. 1.5 × 10 18 Hz ; b. X-rays

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Find the frequency range of visible light, given that it encompasses wavelengths from 380 to 760 nm.

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(a) Calculate the wavelength range for AM radio given its frequency range is 540 to 1600 kHz. (b) Do the same for the FM frequency range of 88.0 to 108 MHz.

a. The wavelength range is 187 m to 556 m. b. The wavelength range is 2.78 m to 3.41 m.

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Practice Key Terms 9

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Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
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