WAVES AND VIBRATIONS


Objects of movement--a bobbing boat, swaying bridge, sound-making flute, pendulum--all involve patterns of movement that can be applied and described in similar ways. Vibrations are described in terms of their frequency (how many times per second the object moves back and forth) and amplitude (how large are the swings?).

Mechanical waves include sound, ultrasound, water waves and seismic waves. All are alike in that they involve moving a vibration through some kind of medium. Waves are vibrations that set up a traveling disturbance, spreading away from its source.

Electromagnetic waves differ from mechanical waves in that the "vibrations" occur in electrical and magnetic fields. Visible light, ultraviolet and infrared light ("heat waves"), microwaves, radio waves and TV signals, X-rays and gamma rays are all electromagnetic waves, differing from one another only in wavelength and in frequency. In combination, they make up the electromagnetic spectrum. Human senses can pick up only visible light and use of technologies such as: photograph film, "night vision" devices, Geiger counters, and radio receivers, detect many other wavelengths.

In addition, waves travel at different velocities. Wave velocities are measured in meters per second. Light waves travel at a faster velocity than sound waves.

(WRESA, Stanks Helen (1995) Guide to Model Assessment)