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Test prep for ap courses

The correct ordering from least to greatest wavelength is:

  1. ELF, FM radio, microwaves, infrared, red, green, ultraviolet, x-ray, gamma ray
  2. ELF, FM radio, microwaves, infrared, green, red, ultraviolet, x-ray, gamma ray
  3. gamma ray, x-ray, ultraviolet, red, green, infrared, microwaves, FM radio, ELF
  4. gamma ray, x-ray, ultraviolet, green, red, infrared, microwaves, FM radio, ELF

(d)

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Describe how our vision would be different if we could see energy in what we define as the radio spectrum.

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Section summary

  • The relationship among the speed of propagation, wavelength, and frequency for any wave is given by v W = size 12{v rSub { size 8{W} } =fλ} {} , so that for electromagnetic waves,
    c = , size 12{c = fλ} {}
    where f size 12{f} {} is the frequency, λ size 12{λ} {} is the wavelength, and c size 12{c} {} is the speed of light.
  • The electromagnetic spectrum is separated into many categories and subcategories, based on the frequency and wavelength, source, and uses of the electromagnetic waves.
  • Any electromagnetic wave produced by currents in wires is classified as a radio wave, the lowest frequency electromagnetic waves. Radio waves are divided into many types, depending on their applications, ranging up to microwaves at their highest frequencies.
  • Infrared radiation lies below visible light in frequency and is produced by thermal motion and the vibration and rotation of atoms and molecules. Infrared’s lower frequencies overlap with the highest-frequency microwaves.
  • Visible light is largely produced by electronic transitions in atoms and molecules, and is defined as being detectable by the human eye. Its colors vary with frequency, from red at the lowest to violet at the highest.
  • Ultraviolet radiation starts with frequencies just above violet in the visible range and is produced primarily by electronic transitions in atoms and molecules.
  • X-rays are created in high-voltage discharges and by electron bombardment of metal targets. Their lowest frequencies overlap the ultraviolet range but extend to much higher values, overlapping at the high end with gamma rays.
  • Gamma rays are nuclear in origin and are defined to include the highest-frequency electromagnetic radiation of any type.

Conceptual questions

If you live in a region that has a particular TV station, you can sometimes pick up some of its audio portion on your FM radio receiver. Explain how this is possible. Does it imply that TV audio is broadcast as FM?

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Explain why people who have the lens of their eye removed because of cataracts are able to see low-frequency ultraviolet.

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How do fluorescent soap residues make clothing look “brighter and whiter” in outdoor light? Would this be effective in candlelight?

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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 or infrared and X-rays).

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Why don’t buildings block radio waves as completely as they do visible light?

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Make a list of some everyday objects and decide whether they are transparent or opaque to each of the types of electromagnetic waves.

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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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