A wave is a disturbance traveling through a medium. In a transverse wave, the displacement is perpendicular to the direction of travel. In a longitudinal wave, the displacement is parallel to the direction of travel.

A wave is characterized by:

• Wave speed: How fast it travels through the medium.

• Wavelength: The distance between two neighboring crests.

• Frequency: The number of oscillations per second.

• Amplitude: The maximum displacement.

《 LOOKING BACK Sections 15.1-15.2 Properties of simple harmonic motion

Yes! Very important waves.

• Sound waves are longitudinal waves.

• Light waves are transverse waves.

The colors of visible light correspond to different wavelengths.

They do. The rate at which a wave delivers energy to a surface is the intensity of the wave. For sound waves, we’ll use a logarithmic decibel scale to characterize the loudness of a sound.

The frequency and wavelength of a wave are shifted if there is relative motion between the source and the observer of the waves. This is called the Doppler effect. It explains why the pitch of an ambulance siren drops as it races past you.

Waves are literally everywhere. Communications systems from radios to cell phones to fiber optics use waves. Sonar and radar and medical ultrasound use waves. Music and musical instruments are all about waves. Waves are present in the oceans, the atmosphere, and the earth. This chapter and the next will allow you to understand and work with a wide variety of waves that you may meet in your career.