Browse Definitions :
Definition

wave number

The term wave number refers to the number of complete wave cycles of an electromagnetic field (EM field) that exist in one meter (1 m) of linear space. Wave number is expressed in reciprocal meters (m-1).

The wave number for an EM field is equal to 2 pi divided by the wavelength in meters. (In some references, it is defined as the reciprocal of the wavelength in meters; in still others, it is defined as the reciprocal of the wavelength in centimeters.) As the wavelength grows shorter, the wave number becomes larger.

Wave number is usually specified for an EM field in a vacuum, also called free space. In most situations, the air is equivalent to a vacuum. In media other than free space, the wave number for a given EM field may increase. When a ray of light passes from air into water or glass, or a radio signal propagates through a polyethylene dielectric rather than air, the wavelength is shortened because the speed of propagation decreases. This causes the wave number to increase.

In free space, the wave number k (in reciprocal meters) is related to the frequency f (in hertz) according to the following formula:

k = f/c

where c is the speed of EM propagation in free space, approximately equal to 2.99792 x 108 meters per second.

In media other than free space, c must be multiplied by a velocity factor v. The velocity factor for a particular medium is the ratio of the speed of EM propagation in that medium to the speed of EM propagation in free space. As such, the velocity factor is always greater than 0 and less than or equal to 1. Taking velocity factor into account, the above formula becomes:

k = f/(vc)

This was last updated in September 2005
• ISO 31000 Risk Management

The ISO 31000 Risk Management framework is an international standard that provides businesses with guidelines and principles for ...

• pure risk

Pure risk refers to risks that are beyond human control and result in a loss or no loss with no possibility of financial gain.

• risk reporting

Risk reporting is a method of identifying risks tied to or potentially impacting an organization's business processes.

• What is risk mitigation?

Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

• fault-tolerant

Fault-tolerant technology is a capability of a computer system, electronic system or network to deliver uninterrupted service, ...

• synchronous replication

Synchronous replication is the process of copying data over a storage area network, local area network or wide area network so ...

Close