5. Properties of waves

Worksheet

Parts of a Wave

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Part 1

In the diagram below, identify the parts of a wave and then give a definition of each term

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Crest / trough / line of origin / wavelength / amplitude

 

crest               5 it is the highest point in a wave

trough            2 it is the lowest point in a wave

line of origin   1 it is the rest position of the matter

wavelength      3 it is the distance between one point on a wave and the exact same place on the next wave

amplitude.      4 how far the medium moves from rest position

Part 2

State which of the following waves you think has the highest frequency and which might have the lowest frequency. Explain the reasons for your selections.

wave #	crest	Trough	wavelength
1	1 cm	1 cm	2 cm
2	3.5 cm	3.5 cm	2.5 cm
3	0.5 cm	0.5 cm	3 cm
4	2 cm	2cm	0.5 cm

(Perhaps it would be useful for you to draw, on graph paper, the four different waves )

Frequency is inversely proportional to the wavelength, then, the wave which has the highest frequency is the wave number 4, and the wave which has the lowest frequency is the wave number 3

Waves

A wave is a disturbance that carries energy from one place to another.

Matter is NOT carried with the wave! A wave can move through matter (a medium). If it must have a medium, it is called mechanical wave. If it can travel without a medium (such as in space), it is called an electromagnetic wave.

Wave Types

1.      Transverse waves: Waves in which the medium moves at right angles to the wave direction.

Parts of a transverse wave:

Crest: the highest point of the wave

Trough: the lowest point of the wave

2.      Compressional (longitudinal) wave: Waves in which the medium moves back and forth in the same direction as the wave.

Wave properties depend on what type of energy makes the wave.

Wavelength: The distance between one point on a wave and the exact same place on the next wave.

1.      Frequency: How many waves go past a point in a second; measured in Hertz (Hz). The higher the frequency, the more energy in the wave.

2.      Amplitude: How far the medium (crests and troughs, or compressions and rarefactions) moves from rest position (the place the medium is when not moving). The more energy a wave carries, the larger its amplitude.

3.      Wave speed: Depends on the medium the wave is traveling in. This varies in solids, liquids and gases.

            Equation for calculating wave speed:

            Wave speed = wavelength (in m) x frequency (in Hz)

Problem:

If a wave has a wavelength of 2 m and a frequency of 500 Hz, what is its speed? Answer: wave speed = 1000 m/s