A wave allows energy to be transferred from one point to another without any particle of the medium travelling between the two points.

Wave motion can be classified base on:

- Mode of Propagation

The class of waves under this are

Mechanical wave: this requires a material medium for propagation

Electromagnetic wave: This travels in a vacuum

- Mode of vibration

The class of waves under this are:

Longitudinal waves

Transverse waves

Diagramatic representation of waves

Definition of terms

Period (T): it is the time taken for a particle to undergo one complete cycle of oscillation.

Frequency (f): it is the number of oscillations performed by a particle per unit time.

Wavelength (λ): it is the distance between any two successive particles that are in phase, e.g. it is the distance between 2 consecutive crests or 2 troughs.

Wave speed (v): The speed at which the** **waveform travels in the direction of the propagation of the wave.

Wave front: A line or surface joining points which are at the same state of oscillation, i.e. in phase, e.g. a line joining crest to crest in a wave.

Displacement : it is the Position of an oscillating particle from its equilibrium position.

Amplitude: it is the maximum magnitude of the displacement of an oscillating particle from its equilibrium position.

**To deduce V = fλ**

no of cycle = n

time = Tn

distance = **λ**n

substitute all into the velocity = distance/time

Note

F is the frequency and the S.I base unit is Hertz(Hz)

T is the period and the S.I base unit is second(s)

**λ** is the wavelength and the S.I base unit is meter(m)

therefore,

** V = fλ**

Displacement-distance graph and Displacement-time graph

The first graph is a displacement-distance graph. On this graph you can find wavelenght and amplitude

The second graph is a displacement-time graph. On this graph you can find period, frquency and amplitude

The only difference between the two graphs is what you can calculate from it.

Phase difference: this is an amount by which one oscillation leads or lags behiod another. it measures in degree or radian.

Phase difference between waves that are exactly out of phase is π radians or 180 degrees

progressive wave: it is a propagation of energy as a results of vibrations of waves which move energy from one place to another.

Intensity: it is defined as power incident per unit area. The intensity of wave generally decreases as it travels along. The two reasons for this are:

- The wave may spread out
- The wave may be absorbed or scattered

As wave spread out, its amplitude decreases

The unit of intensity is

I is the intensity

A is amplitude

f is frequency

r is the distance from the source

Difference between Longitudinal waves and Transverse waves

Transverse waves: A wave in which the __oscillations of the wave particles__ are * perpendicular* to the

__direction of the propagation of the wave__. Light wave is an example of transverse waves

Longitudinal waves: A wave in which the __oscillations of the wave particles__ are * parallel *to the

__direction of the propagation of the wave. Sound wave is an example of longitudinal wave__

Transverse waves can be plane polarised while longitudinal waves cannot be plane polarised.

Electromagnetic waves travel with the same speed in space

the speed of electromagnetic wave is

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