General Wave Properties

General Wave Properties

Introduction
When you hear about waves what comes into your mind? What are some of the examples of waves you know? Where do they occur?
Nowadays you use a number of wireless devices such as phones, radios, televisions and remote controls. Did you know that they also use waves to operate? In this chapter you should be able to investigate the properties of transverse and longitudinal wave forms and explain how waves transmit energy.

4.1: Waves

Key question: Describe how waves are formed.
What you need: Water, basin, a piece of chalk, ICT resource.
Initial question: What is a wave?
What to do (in groups):

1. Pour water in the basin and leave it to settle.
2. Gently drop the piece of chalk in the water and state your observation
   Conclusion and Application)
   3.What happens to the water surface when a piece of chalk falls in water?
   4.Compare the direction of motion of the water particles and the disturbance caused by dropping the piece of chalk in water.
   5.Describe the motion of the disturbance from the point where the piece of chalk drops into the water.
   6. What happens to the surface of water after sometime? Explain.
   7. Basing on the observations made, describe how waves are formed.
   8. Explain how the waves transmit energy through the water.
   Give some other examples of waves which commonly occur in everyday life.

4.1.1: Features of Waves
You always see a number of waves such as those created in water or in ropes,
what general features do they have in common?
Activity 4.2 | Identifying the features of a wave Key question: Explain the features of a wave.
What you need: ICT resource.
Initial question: State any three(3) features of a wave

What to do (In groups):

1. Make research about features of a transverse wave.
2. Study Figure 4.1 and answer the questions in a note book

Conclusion and Application

3. Explain the meaning of the following features of waves;
   (a) Period
   (b) Amplitude
   (c) Crest
   (d) Trough
   (g) cycle
   (e) Equilibrium position
   (h) wave velocity
   (f) Frequency
   (i) wave length
   4.Identify the features named in step (3) in the graph shown in Figure 4.1.
   5.What is the relationship between the frequency, velocity and wavelength of a wave?
   6.How is the knowledge about frequency of radio waves important in daily life?

Self Check

1. Calculate the velocity of a wave with a frequency of 20 Hz and wavelength of 2.0 m.
2. Calculate the frequency of sound waves moving at a speed of 1500 ms-l in a fluid of density 1200 kgm-3 if its wave length is 0.8 m.
   Given that the wave length of a wave of a sound wave moving at a speed Of 100 ms-l is 42 cm. Calculate the frequency of the wave.

4.1.2: Transverse and Longitudinal Waves
Activity 4.3 Investigating the difference between transverse
and longitudinal waves
Key question: Explain the difference between particle motion and direction
of propagation of a wave through a medium.
What you need: ICT resource, rope (about 2 m) and a slinky spring.
Initial question: What is a mechanical wave?
What to do (In groups):

1. Use the rope and the slinky spring to demonstrate transverse and
   longitudinal waves.
2. Draw illustrations to represent transverse and longitudinal waves.
   ‘Conclusion and Application
   3.What do you understand by a;
   (a) Transverse wave?
   (c) Longitudinal wave?
   (b) Compression?
   (d) Rarefaction?
   Explain the difference between transverse and longitudinal waves.
   Discuss the characteristics of mechanical waves.
   Give examples of transverse and longitudinal waves.
   Conduct a research about transverse and longitudinal waves.

4.2: Properties of Waves
4.2.1: Reflection and Refraction of Waves
Activity 4.4 Investigating the reflection and refraction of waves
Key question: Explain the changes which take place when a wave undergoes reflection or refraction
What you need: Ripple tank, power source, stroboscope, wooden bar, straight and curved barriers, microscope slides glued together.
Initial question: What is meant by reflection and refraction of a wave?
What to do (In groups):

1. Make research about reflection and refraction of waves.
2. Using a ripple tank carry out an investigation to demonstrate how waves are reflected or refracted by straight and curved barriers.
   Figure. 4.2 A ripple tank.

3.When does;
(a) Reflection of waves occur?
(b) Refraction of waves occur?
5.Explain how reflection or refraction affects the;
(a) Frequency
(b) Speed
(c) Wavelength of the wave
5.Copy and complete the diagram in Figure 4.3 to show how the waves will be reflected or refracted.

6. Suggest application of reflection and refraction of waves in everyday life.
   4.2.2: Diffraction and Interference of Waves
   Activity 4.5 Investigating diffraction and interference of waves
   Key questiOn: Describe how waves are diffracted or interfered.
   What you need: Ripple tank, power source, stroboscope, and two straight barriers Initial question: What is diffraction?
   What to do (In groups):
7. 1.Make research about diffraction and interference of waves.
   2′ Generate waves in a ripple tank using a straight edge with a straight barrier and observe what happens.

3. Generate water waves using a spherical dipper and observe.
   Conclusion and Application
4. VVhen does;
   (a) Diffraction of waves occur?
   Interference of waves occur?
   (b)
5. Distinguish between constructive and destructive interference.
6. State the conditions necessary for interference to occur.
7. Copy and complete the diagrams in Figure 4.4 to show how the waves

8. Explain why you are able to hear sound from the next classroom even when it is closed.
   4.3: Electromagnetic waves
   Did you know that we are surrounded by a number of invisible waves? Yet they enable you to do a lot of things. For instance, when you call your mother or friend using a mobile phone, what transfers the information? What do you think enables you to change television channels using a

4.3. I: Types of Electromagnetic waves
Activity 4.6 Understanding the types of Electromagnetic waves
What you need: ICT resource, relevant text book and other reading materials
Initial question: What are electromagnetic waves?
What to do (In groups):

1. Make research about electromagnetic waves and their properties.
2. Organise your work and present to class.
   Conclusion and Application
3. What is a vacuum?
4. Mention the types of electromagnetic waves?
5. Explain how electromagnetic waves travel.
6. Discuss the properties of electromagnetic waves.
7. Distinguish between electromagnetic waves and mechanical waves?
8. Explain the electromagnetic spectrum.
9. What are the effects of over- exposure to high frequency radiation.
10. State the electromagnetic radiation which help you do the activities
    shown in Figure 4.5.

11. Suggest other uses of electromagnetic waves.
    44.2: White light and Laser light
    Activity 4.7 Distinguishing between white light and light from a laser
    Key question: Explain the difference between white light and laser light.
    What you need: ICT resource, relevant text books.

Initial question: What are the components of white light?
What to do (in groups):

1. Make research on white light and light from a laser.
2. Organise your work on charts and present to class or use a power point presentation software.
   i Conclusion and Application
3. State the differences between white light and laser light.
4. Suggest the uses of;
   (a) white light
   (b) light from lasers
5. State the dangers of light from lasers.

Chapter 4 Summary
In this chapter, you have learnt that;
A wave is a disturbance that travels in a medium with the capability of transmitting energy from one location to another. These disturbances are either mechanical or electromagnetic in nature.
Electromagnetic waves do not necessarily require a material medium for their propagation as opposed to mechanical waves such as sound waves.
Light waves travel faster than sound waves and therefore waves of higher frequency travel faster as compared to waves of lower frequency.
A ripple tank is an instrument used to clearly demonstrate wave properties which include reflection, refraction, diffraction, and interference.

• White light is composed of a range of frequencies which correspond to various colours that make up the spectrum.
  Laser light is made up of only one that is why it is made up of one colour.