Question

What is the number of waves in one metre defined as?
(A) Wavelength
(B) Wave number
(C) Frequency
(D) Time period

Answer 1

Hint
A wave is a propagating dynamic disturbance in a medium. It travels with the help of crests and troughs that are the highest and the lowest points in a wave, respectively.

Complete step by step answer
A wave is a disturbance or variation that transfers energy progressively from point to point in a medium. It is capable of taking the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential, or temperature.Waves are of two types: longitudinal and transverse. Transverse waves are similar to the surface of water as it is going up and down, and longitudinal waves are like those of sound, consisting of alternating compressions and rarefactions in a medium.
As we know that a wave travels between crests and troughs, when the wave moves from one maximum to another maximum, or one minimum to another minimum, it is said to complete one cycle.
The wavelength is defined as the distance between two successive troughs or crests. Its SI unit is metres. Frequency of waves is the number of waves that pass a point in unit time. And the time period is the time taken to complete one cycle of the wave. Wavenumber is the number of waves per unit distance and is measured in cycles per unit metre.
Hence, the correct answer is option (B); Wave number

Note
Waves are responsible for the transfer of energy through space and matter alike. Light is an electromagnetic wave which we are able to see. Other electromagnetic waves are radio waves and X-rays that serve important purposes in telecommunication and medical industry, respectively.