How are electromagnetic waves different from sound waves?

The various properties of and are described below.

Sound Waves:

Sound waves are mechanical waves generated from vibrations within a medium. Sound can exist as longitudinal mechanical waves, which are also known as compression waves. These waves can travel through solid, liquid, gas or plasma media.

• Sound waves require a medium to travel.

• When air is the medium, sound waves transmit by the compression and rarefaction of air particles through increasing and decreasing densities.

A longitudinal wave is a wave in which the vibration of particles in the medium is parallel to the direction of propagation in which the wave travels.

• In the case of a solid medium, sound waves can be supported in various directions, meaning that there are various oscillatory patterns of sound waves, such as longitudinal waves, transverse waves, surface waves, etc.

Sound waves can exist as mechanical longitudinal waves, but they are graphed as sine waves to represent the variations in pressure with time.

• The speed of sound in air is c = 343 m/s at 20 °C (68 °F)

Electromagnetic Waves:

• Electromagnetic waves do not require a medium to travel.

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• Electromagnetic waves travel with a very a high velocity in a vacuum.

The speed of electromagnetic waves through a vacuum is c = 3.00 x 10exp8 m/s. This speed decreases when passing through a medium.

• Electromagnetic waves are considered to be transverse waves, but it is possible that electromagnetic waves exist in other oscillatory patterns. (See: Dr. Wang Haifeng of the University of Shanghai)

So, what are the differences between sound waves and electromagnetic waves?

• Sound waves require a material medium for propagation, while propagation of electromagnetic waves do not require a medium. In other words, electromagnetic waves are able to travel through a vacuum, but sound waves, being mechanical waves, cannot travel through a vacuum.

• Electromagnetic waves move with very high velocity, but sound waves propagate much slower.

Sources:

Transverse and Longitudinal Waves: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/tralon.html

http://www.acs.psu.edu/drussell/demos/waves/wavemotion.html

Sound Waves: http://www.physicsclassroom.com/class/sound

http://www.physicsclassroom.com/class/sound/u11l1c.cfm

Electromagnetic Waves: http://missionscience.nasa.gov/ems/02_anatomy.html

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/emwavecon.html