Wave Parameters

Amplitude

Amplitude – the amplitude (A) of a wave is the maximum displacement of a particle from its equilibrium position.

Wavelength

Wavelength – the wavelength (λ) of a wave is the minimum distance in which the wave repeats itself.

For a transverse wave, it is the distance between two successive crests or two successive troughs.

For a longitudinal wave, it is the distance between successive compressions or successive rarefactions.

Generally, it is the distance between any two successive points on adjacent waves.

Period

All the particles within a medium, through which a wave propagates, vibrate or oscillate.

Period – the period (T) of a wave is the time taken by a particle to complete one oscillation.

It is the time taken to produce one complete wave.

S.I. unit: second (s).

Frequency

Frequency – the frequency (f) of a wave is the number of oscillations completed by a particle per unit time.

It is the number of complete waves produced in one second.

It is numerically equal to the reciprocal of the period of the wave.

f = 1/T

S.I. unit: s-1 (Hz)

Speed

Speed – the speed (v) of a wave is the distance travelled per unit time.

Since the wave travels a distance of one wavelength (1λ) in one period (1T), the wave speed is given by:                                                                                                                                                                v = λ/T è v = f λ

(f = 1/T) 

Phase Shift

Phase shift – the phase shift (Φ) of a wave gives the current position of the wave relative to the reference position (i.e. the origin).

It is usually expressed in terms of degrees or wavelengths, where 360° corresponds to one wavelength (1λ).                                                                                                                                                  360° à 1λ

180° = λ/2

90° = λ/4

etc.

Example: 

If at times t1 and t2 the position of a particular wave along the horizontal axis is given by the graphs below: 

(i)              [insert PICTURE 4-6] 

(ii)              [insert PICTURE 4-7] 

At time t2, the position of the wave has shifted by a half of a wave, i.e. by a half of a wavelength. Therefore,                                                                                                                                                             Phase difference = λ/2 = 180°