Revision:GCSE Physics: Waves

TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Physics > Waves

What is a wave?

A wave is a vibration or an oscillation, a to and fro motion, which is transmitted through a material or through space. Waves can transfer energy and information from one place to another without the transfer of physical matter. There are some properties of waves that are common to different types of wave such as sound, light and radio waves. But there are also ways in which these waves behave differently.

Longitudinal and transverse waves

Waves can be classified as either longitudinal or transverse, depending on the direction of the vibrations compared to the direction of the wave travel. In a transverse wave, the vibrations are perpendicular to the direction of wave travel. In a longitudinal wave, the vibrations are parallel to the direction of wave travel. Sound waves are longitudinal, light and other electromagnetic waves are transverse.

Wave properties

Wave measurements and the wave equation

These measurements apply to all waves:

• The amplitude of a wave motion is the greatest displacement (change in position) from the rest position.

• The wavelength is the length of one complete cycle of a wave motion. A “squash” and a “stretch” for a longitudinal wave and a “peak” and a “trough” for a transverse wave.

• The frequency of a wave is the number of vibrations each second. Frequency is measured in Hertz.

The relationship between the frequency and the time for one oscillation is:

Frequency = 1/time

Increasing the frequency of a wave causes a decrease in the wavelength. High-frequency waves have short wavelengths, and low-frequency waves have long wavelengths. Frequency and wavelengths are related to the wave speed by the wave equation.

Wave equation

For all waves, the relationship between wavelength and frequency is:

Speed = frequency x wavelength

Amplitude and frequency

The pitch and loudness of a sound are determined by the frequency and amplitude of the wave:

• Increasing the amplitude increases the loudness of a sound. A high-amplitude wave sounds louder than one with a lower amplitude.

• Increasing the frequency increases the pitch of a sound. A high-frequency sound waves has a higher pitch than a low-frequency wave.

Humans can detect sound within the frequency range 20 Hz (Hertz) to 20,000 Hz, but the upper limit is reduced with increasing age.

Compression waves above the maximum frequency that humans can detect are called ultrasound.

--Imsoacademic-191215 11:56, 30 May 2009 (BST)