AST 1002: "Study Guide" Table 8

[Sections Taught by Prof. H.L. Cohen]

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Last updated January 1, 2003
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Table 1 Table 2 Table 6b Table 8 Table 8b Table 8c Table 19
Table 8. The Electromagnetic Spectrum
Designation(1) Wavelength
(nanometers)(2)
Frequency(3)
(lower limit)
Photon
Energy
Atmospheric
Transparency
Gamma Rays    < 0.1 nm   (Very Small) (Enormous) (Enormous) Very Poor
X Rays 0.1-10 nm Very Poor
Ultraviolet 10-380 nm Poor
Visible (Light)(4) 380-750 nm (5) Excellent
   Violet 380-420 nm (Violet Wavelengths About 1/2 Red Wavelengths)
   Indigo(6) 420-450 nm
   Blue 450-490 nm
   Green 490-570 nm
   Yellow 570-590 nm
   Orange 590-630 nm
   Red 630-750 nm (Red Wavelengths About 2 times Violet Wavelengths)
Infrared 750 nm-0.1 mm Poor
Microwave(7) 0.1 mm-10 cm Fair to Good
Radio(8) over 10 cm   (Very Large) (Small)
(less than 3,000 MHz)
(Very Small) Very Good
   FM Radio 2.8-3.4 m 108-88 MHz   (Poor over 10 m)
   AM Radio 190-560 m 1,600-540 MHz    

Table Notes

  1.  All E-M radiation travels at the same speed through a vacuum (300,000 km/sec or 186,000 mi/sec).
  2.  A nanometer equals one billionth (10-9) of a meter or ten Ångstroms (Å), a unit often used to specify the size of wavelengths. (For example, 400 nm = 4000 Å.)
  3.  Frequency equals the number of waves passing per second (frequency and wavelength are inversely related); historically the unit of frequency was the cycle (wave) per second now called a hertz (Hz). MHz = 1 million Hz.
  4.  Visible (light) is often called the visible or optical window because light easily passes through air (see last column of table).
  5.  Notice the range of visible wavelengths is about a factor of two (from just under 400 nm for violet to just over 700 nm for red).
  6.  Indigo is often grouped with violet and blue.
  7.  Microwaves are often grouped with long infrared waves and short radio waves.
  8.  Radio is often called the radio window because radio easily passes through air (see last column of table).

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