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Oscillations and Waves

- Wave Characteristics

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Progressive Waves Any wave that moves through or

across a medium (e.g. water or even a vacuum)

carrying energy away from its source is a

progressive (travelling) wave. E.g. A duck on

water As the wave passes the duck, the

water (and duck) only oscillate vertically.

This illustrates that there is no net transfer of

the medium through which the wave travels, only

energy moves from place to place. In many

examples, the wave carrying medium will oscillate

with simple harmonic motion (i.e. a ? -x).

Types of Wave Waves can be described as

transverse or longitudinal. In a transverse wave

the vibration (oscillation) of particles is at

right angles to the direction of energy transfer.

Transverse waves cannot move through a gas.

Examples In a longitudinal wave the vibration

of particles is in the same plane as the

direction of energy transfer. Examples

Transverse Longitudinal

(Label a crest (peak), trough, rarefaction,

compression)

Describing Waves Crest and trough Points on the

wave where particles are oscillating at maximum

positive and negative displacement. Rarefaction

and compression Areas in a longitudinal wave

where particles are far apart (lower than normal

density) and close together (higher than normal

density).

- Wave graphs
- Waves can be represented graphically in two ways
- Displacement - Distance
- Displacement Time

The following terms and descriptions are mixed

up. Copy the table but give each term the correct

description Intensity of a wave is the

power per unit area incident upon a surface, in

Wm-2. (It is proportional to the square of the

amplitude, so I ? A2)

Term Description

1. Wavelength (?) a. The maximum displacement from the equilibrium position (in metres, m)

2. Amplitude (A) b. The distance moved by a wave crest per second (in metres per second, ms-1)

3. Frequency (f) c. The time required for the wave to complete one oscillation (in seconds, s)

4. Periodic Time (T) d. The distance between two successive crests (in metres, m)

5. Speed (v) e. The number of waves completed in one second (in Hertz, Hz)

Term Description

1. Wavelength (?) d. The distance between two successive crests (in metres, m)

2. Amplitude (A)

3. Frequency (f)

4. Periodic Time (T)

5. Speed (v)

Term Description

1. Wavelength (?) d. The distance between two successive crests (in metres, m)

2. Amplitude (A) a. The maximum displacement from the equilibrium position (in metres, m)

3. Frequency (f)

4. Periodic Time (T)

5. Speed (v)

Term Description

1. Wavelength (?) d. The distance between two successive crests (in metres, m)

2. Amplitude (A) a. The maximum displacement from the equilibrium position (in metres, m)

3. Frequency (f) e. The number of waves completed in one second (in Hertz, Hz)

4. Periodic Time (T)

5. Speed (v)

Term Description

1. Wavelength (?) d. The distance between two successive crests (in metres, m)

2. Amplitude (A) a. The maximum displacement from the equilibrium position (in metres, m)

3. Frequency (f) e. The number of waves completed in one second (in Hertz, Hz)

4. Periodic Time (T) c. The time required for the wave to complete one oscillation (in seconds, s)

5. Speed (v)

Term Description

1. Wavelength (?) d. The distance between two successive crests (in metres, m)

2. Amplitude (A) a. The maximum displacement from the equilibrium position (in metres, m)

3. Frequency (f) e. The number of waves completed in one second (in Hertz, Hz)

4. Periodic Time (T) c. The time required for the wave to complete one oscillation (in seconds, s)

5. Speed (v) b. The distance moved by a wave crest per second (in metres per second, ms-1)

The Wave Equation In a time of one full period (t

T), a point in a wave will move forward through

one a distance of one whole wavelength (d

?). so substituting gives This is called

the wave equation

Speed Distance Time

Wave speed Wavelength Time period

v ? T

but T 1 f

v f ?

- Electromagnetic Waves
- The visible spectrum of light (Roy G Biv) is just

a small part of a larger group of electromagnetic

waves known as the electromagnetic spectrum. - All electromagnetic radiation
- exists as variations in electrical and magnetic

fields - travels at 3 x 108 ms-1 (300 000 000 ms-1)
- can travel through a vacuum
- carries energy
- has wave behaviour (obeying v f?)

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