This document discusses wave properties and motion. It defines key wave terms like amplitude, wavelength, frequency, period, and speed. It explains that waves transfer energy without transferring matter and compares two main types of waves: transverse waves where particles vibrate perpendicular to the direction of travel, and longitudinal waves where particles vibrate parallel to travel. Examples of each type are given. Formulas showing the relationships between wave speed, frequency, and wavelength are provided.

1. General Wave Properties

2. Before we move on, We have… Representing the video clips available Representing the applets available Representing the websites available

4. Lesson Trigger W aves are disturbances that travel away from its source of origin, the centre of disturbance. It is one way by which energy can be transmitted from one place to another. Waves, Waves, Waves Sound waves carry sound energy from the source (for e.g., loudspeaker) to the receiver (ear). Example : Go to Exp9b.mpg What are waves? What can waves do? hyperlink

5. Sound waves carry sound energy from the loudspeaker to our ear. In doing so, what are being disturbed? Pause and Think The air molecules between the loudspeaker and the receiver are being disturbed. Go to Exp9b.mpg air molecules are pushed back and forth between the loudspeaker and the ear.

6. Waves can take many forms, but there are 2 fundamental types of waves: Let’s study the wave motions to distinguish these two types of waves. Wave classification 1 Transverse waves 2 Longitudinal waves Go to E-SimPhy_302.exe both waves differ in the way the particles in the medium behave. hyperlink

7. Such wave motion produces transverse waves. Are the air particles being moved away from the disturbance centre ? No, only wave energy is transferred, the particles do not move away from the disturbance centre Transverse Wave motion Where is the disturbance centre? When a wave is generated, its propagation is seen as a travel of the disturbances from the disturbance centre. How do the particles in the medium respond? The particles vibrate up and down, perpendicular to the direction of wave travel. Go to E-SimPhy_302.exe wave travels from left to right.

8. Are the air particles in the medium transferred away from the disturbance centre? As in transverse waves, the particles do not move away from the disturbance centre, only the wave is transferred. How do the particles in the medium respond? The particles vibrate to and fro, parallel to the direction of wave travel. Such wave motion produces longitudinal wave. As the longitudinal waves travel towards the right, the particles in the medium is disturbed. Longitudinal Wave motion Wave travels from left to right.

9. Waves transfer energy without transferring matter When waves are generated by an energy source, they are propagated from its centre of disturbance, carrying energy away from it. Waves travels away from energy source. However, while the energy is propagated outwards, the particles in the medium only vibrate about their equilibrium position. Hence, waves transfer energy from one point to another without transferring matter.

16. 5 Frequency f – the number of complete oscillations made by an oscillating particle in one second. – Frequency unit : hertz (Hz). 1 Hz = 1 oscillation per sec 6 Period T – The time taken for the oscillating particle to make one complete oscillation. – Period is measured in second (s). As the wave is propagated, each particle in the medium oscillates back and forth about its equilibrium position. time/s 0 1.0 2.0 3.0 4.0 5.0 6.0 displacement/cm 5.0 5.0 0 Terms used to describe waves

17. If a particle can make many complete oscillations within 1 s, (i) what can you say about its frequency and period? (ii) how are period and frequency related? Finding Relationship T is inversely proportional to f .  its frequency f is high.  its period T will be short. time/s displacement/cm 0 0.1 0.2 0.3 0.4 0.5 0.6 What are the values of the period and frequency of this wave? f = 1 ÷ T = 1 ÷ 0.2 = 5 Hz T = 1 f T = 0.2 s

18. When a ripple tank is used to study wave motion, we can see crests and troughs from the side of a ripple tank. Terms used to describe waves These wavefronts join all crests together. These wavefronts join all troughs together. crest trough Wavefronts refer to imaginary lines drawn to join all points in space that are in the same states of disturbance caused by a wave propagating through a medium.

20. Hence, in 1 period , the distance moved by the wave is 1 wavelength . What is the speed of the wave? v = f  Waves speed formula t = 0 T t = ¼ T t = ½ T t = ¾ T t = 1 T Since: speed = distance time Wave speed = wavelength period  v =  T  1/ f =

21. State the value for (i) amplitude of the wave. ( ii) the wavelength of the wave. (a ) Fig. 1 shows a graph of the variation of the displacement of a wave with distance along the wave at a particular time. (i) a = 0.40 cm (ii)  = 0.20 cm Sample discussion distance/cm 0 0.20 0.40 0.60 displacement/cm 0.40 -0.40 Fig. 1

22. (b) Fig. 2 shows the graph of the variation of the displacement of the same wave with time at a particular point along the wave. Calculate its wave speed. T = 0.10 s f = 1  0.10 = 10 Hz Sample discussion distance/cm 0 0.20 0.40 0.60 displacement/cm 0.40 -0.40 Fig. 1 time/s 0 0.10 0.20 0.30 displacement/cm 0.40 -0.40 Fig. 2 v = f  = 10  0.20 = 2.0 cm/s

23. Summary By the end of this lesson pupils are able to: Describe what is meant by wave motion. Understand that waves transfer energy without transferring matter. Define speed, frequency, wavelength, period and amplitude. State what is meant by the term wavefront. Solve problems using the relationship velocity = frequency  wavelength. Compare transverse and longitudinal waves and give examples of each.