Wave Frequency

Wave motion can be described in terms of frequency as well as wavelength. The frequency of a wave motion is the number of waves that pass by a fixed point in a given time, measured in cycles per second (cps).

The human eye responds to different-color light waves that have very high frequencies. Visible light waves vary in frequency from 4.3 x 1014 cps for red to 7.5 x 1014 cps for violet, with the other colors in between.

For radio waves, one cycle per second is commonly called a hertz (Hz), after the German physicist Heinrich Hertz (1857-1894), who first produced radio waves in a laboratory. An AM radio receives radio waves with frequencies of 550 to 1650 KHz (kilohertz); 1 KHz is 1000 cycles per second. The FM band ranges from 88 to 108 MHz (megahertz); 1 MHz is a million cycles per second.

Refer to the electromagnetic spectrum shown in Figure 2.4. Which waves have (a) a higher frequency than the visible light waves?_

_(b) a lower frequency than the visible light waves?_

Answer: (a) Higher frequency: gamma rays, X-rays, ultraviolet radiation. (b) Lower frequency: infrared radiation, submillimeter waves, microwaves, radio waves.

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