2 wave features (7.2)

Representing Wave Features

If a series of waves were moving in water from left to right, the displacement of the medium (water) can be tracked using a cork. The cork could be seen to be going up and down.

Displacement-distance Graphs

An easy way to show the information in the previous diagram is by using a graph of particle displacement versus distance from the source.

The Speed of Waves

Calculate:1. The average speed of the

wave.2. The horizontal speed of

particle P3. The average vertical speed

of particle P between t = 0 secs and t = 0.025 secs

Solutions

Find the error!!!

Frequency of a Wave

All mechanical waves must have a vibrating source.

The frequency, f, of a source is the number of vibrations (cycles) that are produced each second. i.e. cycles per second.

1 cycle per second = 1 Hertz

Examples of Frequency

• What is the frequency of the second hand of a clock?

Frequency = 1cycle/60 sec Period = 60 sec

What is the frequency of US Presidential elections?

Frequency = 1 election/4 yrs Period = 4 yrs

Period of a WaveThe time interval for one cycle to be completed is called the Period, T,

and is measured in seconds.

The Period of a wave is best seen in a Displacement-Time Graph.

Frequency, f, and Period, T, show an inverse relationship and are connected by the formula:

Where f is the frequency of the wave in hertz (Hz)

T is the period of the wave in seconds (s).

Wavelength The Wavelength, λ, of a continuous wave is the distance

between two successive points of the same displacement and moving in the same direction.

Amplitude

The amplitude, A, of a wave is the maximum displacement of a particle from its mean (average) position.

THE WAVE EQUATION

The Wave Equation

TEXT: Page 239, Nos 6, 7, 9, 10.