1. KS4 Waves: Character

2. Wave Character: Learning Objectives  Understand the nature of wave amplitude, wavelength and frequency.  Be able to calculate and convert between frequency, period, speed and wavelength. Textbook references: Section 6.01, p.124-125 Filepath: I:\Ph\Y11\11.2 Physics - Mr Peter (PEW)\ 11.2 Lesson Notes\Waves Topic\ Lesson 2 - Wave Character

3. Energy and Waves : Review Waves carry energy from one place to another. There are 2 main types of wave you need to know about: Transverse Waves e.g. light waves Longitudinal Waves e.g. sound waves

4. Transverse Waves: Review TRANSVERSE WAVES A transverse wave can be made using a rope between two people like this : What type of energy is the wave transferring? In which direction is the energy moving? In which direction is each part of the rope moving? kinetic

5. Each part of the wave moves at right angles [90º] to the direction the energy is moving in: Particle Movement Energy Movement Transverse Waves : Review TRANSVERSE WAVES

6. ****** Time ****** a a = ****** = ******  Displacement + Transverse Waves: Review TRANSVERSE WAVES

7. Wavelength and amplitude: review What is the wavelength ( ) of a transverse wave? What is the amplitude (a) of a transverse wave? It is the ****** between two ****** points on the wave. It is the ****** of the wave, the bigger the amplitude of the wave, the more ****** it has.

8. Animation to demonstrate wavelength, amplitude and frequency

9. LONGITUDINAL WAVES You can make a longitudinal wave using a spring between two people like this : What type of energy is the wave transferring? In which direction is the energy moving? In which direction is each part of the spring moving? [put a marker on the spring to help you see] ****** Longitudinal Waves : Introduction

10. You should have noticed that each part of the wave moves in the same direction as the direction the energy is moving in: particle movement energy movement When you speak to someone, the air vibrates as a longitudinal wave : LONGITUDINAL WAVES Longitudinal Waves : Review

11. Make a labelled diagram of your spring like this : ******Compression ******Rarefaction LONGITUDINAL WAVES Longitudinal Waves : Review

12. Frequency: Review The number of waves passing a point each second is called ****** [ƒ] Frequency [ƒ] is measured in ****** [Hz] Frequency [ƒ] = Number of waves passed  Time [s] 1 wave per second = 1 Hz If the wave below passes a point in 1 second, what is it’s frequency?

13. Frequency and Period  The period (T) of an oscillation is the time taken for one complete oscillation (measured in seconds – s).  The frequency (f) of an oscillation is the number of oscillations per second (measured in Hertz – Hz)  The relationship between the two is: f = 1 / T or T = 1 / f  Look at the pendulum on the right. By measuring the time taken for 50 swings, can you calculate is period, and hence its frequency?

14. 6 10 1 3 5 0.5 Calculating FrequencyWaveCycles Time (s) Freq (Hz) 2 2 2

15. The Wave Equation = 2m 1 second later : Imagine waves on the sea travelling over a shipwreck:

16. In the diagram, 5 waves pass the shipwreck in 1 second………………….so the frequency = 5 Hz The wavelength [ ] = 2 m This means that the waves travel 10 m in 1 s ……….………………so the speed is 10 m/s So, in this example, the frequencyX wavelength=speed 5X 2= 10 Hz m m/s This is usually written as : Waves : wave speed

17. V =  x For the Extended paper, you will need to be able to change the subject of the formula :  = V  and = V   Waves : wave speed

18. Reminder: Formula triangles v f   x Formula triangles help you to rearrange formula. The triangle for the wave equation is shown below: Whatever quantity you are trying to find cover it up and it will leave you with the calculation required. So if you were trying to find frequency, f….. …you would cover f up… …and you are left with the sum… f = v

19. Wave Speed – complete the table 3.0 0.2 1.32 2.4 0.01

20. Energy and Waves : A Question The photograph shows waves travelling across the surface of a pond. 1m 1)Is this an example of a transverse or longitudinal wave? 2)Estimate the wavelength of the wave: 3)If the frequency of the wave is 0.2 Hz, calculate the speed of the wave: ******

21. What are the units of frequency? A. Metres B. Hertz metres C. Hertz/metres D. Hertz

22. A wave has a wavelength of 6m and a frequency of 5Hz. What is the speed of the wave? A. 1.2 m/s B. 0.88 m/s C. 3.0 m/s D. 30 m/s

23. Wave Character Questions 1. Name two similarities and one difference between transverse and longitudinal waves. Answer: 2. Draw a transverse wave and label the amplitude (A), wavelength ( 2. Draw a transverse wave and label the amplitude (A), wavelength ( ), crest (C), and trough (T).

24. Wave Character Questions 3. 3. The surface of a drum vibrates 300 times in one minute. What is the frequency of the sound wave produced, and how many waves travel out from the drum in 5 seconds? Answer: 4. 4. For the drum in question (3) above, if the speed of sound in air is 330 m/s, what is the wavelength of the sound? Answer:

25. Wave Character Questions 5. 5. Using your textbook and/or the Internet, give three examples each of transverse and longitudinal waves in nature. Answer:

26. Wave Character: Learning Objectives  Understand the nature of wave amplitude, wavelength and frequency.  Be able to calculate and convert between frequency, period, speed and wavelength. Textbook references: Section 6.01, p.124-125 Homework: Textbook page 144, Question 1