5. Properties of waves

Worksheet

Parts of a Wave

.

Part 1

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

.

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

4. Waves

1. What are waves?

Waves are disturbances that transport energy from one location to another, without transportation of matter.

Play with wave!

2. What are mechanical waves?
Are the waves which require a medium to propagate from one point to another.

3. Why can waves propagate?
Because of the interactive forces between particles of a medium.

4. In the 'spring model', what do the springs represent?

Springs represent the interaction forces between the particles of the medium.

5. Can you specify two different types of mechanical waves?

Longitudinal Waves

Transverse Waves

6. Can you define both kinds of waves?

Longitudinal Waves: This kind of waves make the particles of the medium vibrate parallel to the direction of wave motion. Look here an example of longitudinal waves

Transverse Waves: They make the particles of the medium vibrate perpendicular to the direction of wave motion. Look here an example of transverse waves

7. What is 'inertia'?

Inertia is the tendency of objects to resist the change in motion when they are pushed or pulled, look an example of inertia.

8. What kind of particles tend to have more inertia?

Particles which have more inertia are those with more mass.

9. In longitudinal waves, are the particles of the medium carried along by the propagating waves?

The particles of the medium aren’t carried along by the propagating waves because each particle moves left and right in succession as the waves propagate.

10. In longitudinal waves, why don't the particles of the medium move at the same time?

Because the inertia makes particles move in succession and not at the same time.