AST 1002: "Study Guide" Table 8
[Sections Taught by Prof. H.L. Cohen]Site Map Prof. Cohen Department of Astronomy University of Florida
Last updated January 1, 2003
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Table 8. The Electromagnetic Spectrum Designation(1) Wavelength
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
- All E-M radiation travels at the same speed through a vacuum (300,000 km/sec or 186,000 mi/sec).
- 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.)
- 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.
- Visible (light) is often called the visible or optical window because light easily passes through air (see last column of table).
- 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).
- Indigo is often grouped with violet and blue.
- Microwaves are often grouped with long infrared waves and short radio waves.
- Radio is often called the radio window because radio easily passes through air (see last column of table).
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