Waves_and_Wave_Motion

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Waves and Wave Motion

A Wave is a means of transferring from one to another

Transverse waves

A Transverse wave is a wave where the of is to the direction in which the wave .

Examples
1. waves.
2. waves.
3. Waves on a rope.
4. Water waves.

Longitudinal Waves

A Longitudinal Wave is a wave where the of is to the direction in which the wave travels.

Examples
1. waves in a solid, liquid or gas.
2. waves on a spring.


Terms used to describe a wave

The wavelength λ of a wave is the distance from one on the wave to the corresponding point on the next .

The frequency f of a wave is a measure of the number of (vibrations) of the wave per .

The Amplitude A is the distance of any particle from its position.

The Velocity v of a wave is the travelled by one in one .

The periodic time of a wave (T) is the time taken for one complete .

Variable Symbol Unit Symbol for unit

Frequency f or 1 s -1

Wavelength λ m

Velocity v metres / second (m / s)

Periodic Time T s

Relationship between frequency, velocity and wavelength

v = x λ

Relationship between Periodic Time and frequency

T = 1 /

Characteristics of a wave

1. Reflection is the of waves off of an in their path.

2. Refraction is the changing of of a wave as it travels from one to another.

Note that when a wave travels from one medium to another its does not change.

3. Diffraction is the of waves around a or an obstacle.

This effect is only significantly noticeable if the slit width is approximately the same as the wavelength of the waves.

4. Polarisation is when a wave is allowed to in one only. Only waves can be polarised.

5. Interference occurs when from two sources meet and a wave is produced. The new wave produced is the algebraic of the of each individual wave.

Constructive Interference occurs when waves from two sources meet to produce a wave of .

Destructive Interference occurs when waves from two coherent sources meet to produce a wave of amplitude.

Coherent Waves :

Two waves are said to be coherent if they have the same and are in or a constant phase difference.
.
Stationary waves

Stationary waves are formed when periodic travelling waves of the same and amplitude, travelling in directions, meet.

In Stationary waves......

1. The distance between two consecutives is λ / 2

2. The distance between two consecutive is λ / 2

3. The distance between an anti-node and the next node is λ /


The Doppler Effect

The Doppler Effect is the change in the of a wave due to the relative motion between the of the wave and the .

f ' = f c / (c ± u)

Formula:

f ” = frequency
f = frequency
c = speed of the
u = speed of the source


As a moving source moves towards the observer the get closer together.

This means that the is smaller .

This means that the frequency appears to .

As a moving source moves away the observer the get futher .

This means that the wavelength is .

This means that the frequency appears to .


Applications of the Doppler effect:

1. Police traps
2. Measuring the red shift of galaxies in astronomy
3. Ultrasound (blood movement or heartbeat of foetus)