Part 1 Waves carry energy

Transcription

1 Science Stage 5 Gill S Waves Part 1 Waves carry energy S 43932

2 Number: Title: Waves This publication is copyright New South Wales Department of Education and Training (DET), however it may contain material from other sources which is not owned by DET. We would like to acknowledge the following people and organisations whose material has been used: Extract from Science Syllabus Years 7-10 Board of Studies, NSW 2004 Unit overview pp iii-vi Photograph of a man standing on a cliff Rhonda Caddy Part 2 p 11 Photograph of Satellite dish Nova Development Corporation (Art Exploision) Front cover and all part covers 1-4 inclusive COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you on behalf of the New South Wales Department of Education and Training (Centre for Learning Innovation) pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. CLI Project Team acknowledgement: Writer(s): Editor: Illustrator(s): Project Manager(s): Desktop Publisher Rhonda Caddy and Richard Alliband Ric Morante Thomas Brown, Rhonda Caddy, David Evans, Barbara Gurney, Tim Hutchinson Julie Haeusler Alide Schimke All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith. Published by Centre for Learning Innovation (CLI) 51 Wentworth Rd Strathfield NSW 2135 Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of the Centre for Learning Innovation (CLI). State of New South Wales, Department of Education and Training 2005.

3 Contents Part 1 Lesson 1 Energy revision... 3 Energy transformation examples...5 Law of conservation of energy...6 Energy transfer...6 What did you achieve?...6 Lesson 2 Listening to sound waves... 7 What did you achieve?...10 Lesson 3 Sound: energy, vibrations and waves Sound as energy...11 What makes sound vibrations?...13 Why do sound waves need a medium for propagation?...15 What did you achieve?...16 Lesson 4 Types of waves Waves in ropes and springs...17 Water waves...19 Sound waves...21 Electromagnetic waves...24 What did you achieve?...25 Lesson 5 Describing and visualising waves Oscilloscopes...31 What did you achieve?...36 Suggested answers Part Exercises Part Part 1 Waves carry energy 1

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5 Lesson 1 Energy revision This activity is a pretest. It is a quick test to check what you know before you begin the unit. If you find the test easy, you are ready to begin learning about waves as energy carriers. If you don t know some of the answers don t panic the suggested answers will remind you of the concept. Activity: Pretest Circle the best alternative for questions 1 to 4 below. 1 What is energy? a how heavy something is b the ability to make things move or change c the amount of space something occupies d how a machine runs 2 What is matter? a things, such as substances or objects b something you can see c something you can feel or touch d energy 3 Which statement is true? a Energy and matter are the same as each other. b Everything has the same amount of energy. c Only moving things have energy. d Energy can change from one type to another. 4 Which statement is not true? a Light energy can travel from the Sun to Earth. b Sound energy can travel from the Sun to Earth. c A spaceship moving from Earth towards the Sun has kinetic energy. d A rocket contains potential energy to let it blast off from Earth towards the Sun. Part 1 Waves carry energy 3

6 5 There are several different types of energy. Tick the examples below that are types of energy. heat, such as the heat from a fire light, such as the light from the Sun sound, such as the noise from an explosion chemical, such as the energy stored inside food nuclear, such as the energy released by a nuclear reactor electrical, such as the energy used to run a television potential, such as the energy stored in an object lifted up against gravity potential, such as the energy stored in an object bent, stretched or compressed kinetic, such as the energy in the moving parts of a motor. 6 How can energy move from one place to another? Use the names of some of the types of energy to complete these sentences. a b c d energy travels through matter that is a conductor. Sometimes it jumps between conductors as large sparks. energy does not need matter to travel. It can pass through matter that is transparent. energy can only move through matter. It cannot pass through a vacuum. (A vacuum is a space that does not contain any matter.) energy is another type of energy that can move through matter and through a vacuum. Check your responses by going to the suggested answers section. Now consider some examples of energy transformation where energy changes from one form to another. 4 Waves

7 Energy transformation examples 1 Chemical energy in fireworks can be transformed quickly into heat, light and sound energy. 2 Lifting an elephant against gravity requires energy which is transformed into increasing elephant s potential energy. If the elephant falls its potential energy changes to kinetic energy. 3 A bent ruler can change potential energy to kinetic energy. Part 1 Waves carry energy 5

8 Law of conservation of energy One of the most important ideas in science is conservation of energy. By about 1850 scientists became aware that if a certain type of energy disappeared, other types of energy appeared. It became accepted that energy was preserved or saved. Energy could not be created or destroyed. Energy just changes from one form to another (transformation) or is transferred to another location. The total amount of energy does not change. Repeated observations and/or measurements give results that support this idea. Thus the idea of conservation of energy is reliable. This idea is also found to apply with very small objects like atoms, human-sized objects or objects as large as stars and galaxies. It applies universally, that is, throughout the known Universe. An idea like this, that is universally reliable, is called a law. Energy transfer Energy transfer is different from energy transformation. Energy transfer is when energy moves from one location to another. Examples are: heat energy transferring out of your hand on touching cold metal heat from a fire warming a room. Go to the exercises section and complete Exercise 1.1: Revision of energy concepts. What did you achieve? Tick what you can do: describe the difference between matter and energy identify different types of energy distinguish between transformation, transfer and conservation of energy. 6 Waves

9 Lesson 2 Listening to sound waves Sound energy is carried away from its source, the place where it is released, by sound waves. Sound waves need a medium for propagation. This mean that sound waves need to travel through matter. Sound waves from explosions on the Sun s surface cannot reach the Earth. There is just empty space and no matter between the Sun and the Earth. Here on Earth there is usually gas (air), liquid (water) or a solid between your ears and any source of sound. Sound waves can propagate through the matter that surrounds your ears. Listen to the audiofile Fifteen different sounds at and follow the links to Stage 5 Junior Science, Year 9, Waves, Lesson 2. Activity: Observations and inferences Observations are what you detect using your senses sight, hearing, touch, smell and taste. Inferences are different. An inference comes after an observation. An inference is what you think happened. It is based on what you observed and information that you have stored in your brain from past experience. When you hear a sound you are making an observation. Only then can you make an inference. The inference is what you think happened based on observations, knowledge and understanding from past experiences. Listen to the people on the audiofile as they explain the activities that you are going to do. If you do not have access to a computer with Internet connections, then complete the I can t listen section at the end of this lesson. Part 1 Waves carry energy 7

10 There are fifteen different sounds on the audiofile. Observe (listen to) each sound then make an inference; write down what you think is the source of the sound Listen to the sounds again to check your inferences. Check your response by going to the suggested answers section. Now, test how good you are at distinguishing intermingled sounds. 8 Waves

11 Listen to the audiofile People laughing at and follow the links to Stage 5 Junior Science, Year 9, Waves, Lesson 2. Activity: How many people can you hear? How many different voices can you hear? How many people are there? Check your response by going to the suggested answers section. What parts of your body are involved in hearing? Use books or a computer to find out. If you are connected to the Internet go to for some links. What you find out can be used to complete Exercise 1.2: Labelling parts involved in human hearing. I can t listen If you cannot listen to the audiofile, here is a listening activity for you. Activity: I can t listen 1 Listen! Write down five things that you can hear. Part 1 Waves carry energy 9

12 2 Now keep listening. Try to write down another five sounds that you can hear. 3 Turn on the television or radio for two minutes only. Listen but don t watch! In the two minutes that you are listening, how many different voices do you hear? Go to the exercises section and complete Exercise 1.2: Labelling parts involved in human hearing. What did you achieve? Tick what you can do. describe sound energy as a form of energy which requires a medium for propogation identify sounds on an audiofile (or made in your surroundings) distinguish between the sound of different people s voices identify parts involved in human hearing on a diagram. 10 Waves

13 Lesson 3 Sound: energy, vibrations and waves All sound is produced as a result of particles vibrating. Vibrating particles have energy. Sound as energy All forms of energy are able to cause objects to move. Activity: Sound energy produces movement Try this activity to see how sound energy produces movement. What you will need: a balloon What to do: 1 Blow up the balloon. Hold the neck of the balloon firmly between two fingers so that the air cannot escape. Put your other hand on the other end of the balloon. Part 1 Waves carry energy 11

14 2 Now talk to your balloon! Go on. No-one is watching! What did you feel with your hands? You probably felt shaking or vibration. 3 Now tie off the end of the balloon. Hold the balloon between the sensitive tips of the fingers of both hands. Talk quietly, talk loudly and sing to your balloon. What do you observe with vibrations in the balloon when you put more energy into your talking or singing? The more energy that you put into talking or singing, the more sound vibration you detect in the balloon. Sound energy from your voice made the balloon vibrate. 12 Waves

15 What makes sound vibrations? Activity: What makes sound vibrations? Try this activity to help you understand the movements in a vibration. You will need: a ruler a flexible plastic one is best. What to do: Hold the ruler so that about 7 cm of it is on a table and the rest sticks out off the table. Press down firmly so that the end of the ruler on the table does not move. Then flick the other end of the ruler so that it vibrates. Watch carefully to see the way that the ruler moves. What does it do? Did you notice that the ruler bounces up and down? You only flicked it once but it kept going up and down for quite some time. The vibrations of the ruler are similar to the movements of a swing. But it s easier to see what a swing does because it doesn t move so quickly! Part 1 Waves carry energy 13

16 position speed negative maximum zero zero maximum positive maximum zero acceleration maximum zero maximum A swing hangs in the middle. To start the swing, you pull it backwards. Then it goes to the middle, forward, to the middle and back, middle, forward, middle and back, middle, forward, middle and back and if you don t do anything, it eventually stops in the middle again. That s what the ruler was doing, but up and down. And that is what the balloon was doing between your finger tips, vibrating in and out. Vibrations can also cause sound. When a window shakes backward and forwards it makes a rattling sound. Place your finger tips on the middle of the front of your neck and make sounds. You should be able to feel the vibrations in your voice box that produce sounds. Energy, vibrations and sound go together. Go to the exercises section and complete Exercise 1.3: Vibration and sound. This exercise lets you plan and carry out a demonstration to show that vibrations can produce sound waves. 14 Waves

17 Why do sound waves need a medium for propagation? Sound energy travels as sound waves. Sound waves are carriers of sound energy. So, what do sound waves need to travel? Think about when sound waves cannot travel. It is silent out in space because sound waves cannot travel through a vacuum. There must be matter, or substances, for sound to travel. Sound waves can travel through solids, liquids and gases because these things are matter. Why is matter needed? Sound waves move by making matter vibrate. So if there is no matter to vibrate, the sound wave cannot be passed on and the sound energy cannot travel. A reminder about solids, liquids and gases What are solids, liquids and gases like? In solids, particles are packed closely together. In gases, particles are spaced widely apart. In liquids, particles are neither very close or wide apart. These ideas are part of what is called the particle model/theory of matter. Some scientists say that this is the most important model or theory used in science. Part 1 Waves carry energy 15

18 How are solids, liquids and gases alike? Did you say that they all contain particles? Anything that is matter is made up of particles. Particles are needed for sound energy to travel. Sound waves are able to travel most quickly through solids because the particles are very close together. Movement in one particle transfers quickly to the particles next to it. Sound waves travel most slowly through gases since the particles are further apart. What did you achieve? Tick what you can do. show that sound is a form of energy able to produce movement demonstrate how a vibration produces sound plan and perform an activity to show that vibration produces sound waves explain why sound waves can travel through matter but not through a vacuum. Look at the list again. If you haven t ticked all the statements, go back and review the sections where you are not confident. Then, tick the items that you have revised in the check list above. 16 Waves

19 Lesson 4 Types of waves Waves can be of two main types. These are described according to how the motion of the particles or field direction changes compared to the direction in which the wave travels. The activities below will clarify this classification. Waves in ropes and springs Activity: Making waves in a rope What you will need: a rope or thick cord. It doesn t matter how long it is, provided it can wiggle like a snake. What to do: 1 Pull the rope into a straight line. 2 Hold one end of the rope just above the ground and wiggle it from side to side. It probably needs to move about 30 cm each way, going across and back each second. 3 Sketch the shape the rope makes, below. 4 Where does the energy come from to make the wave shape in the rope? Part 1 Waves carry energy 17

20 5 Make the rope straight again. This time, move it across and back once only. What do you notice? Look at the answers in the answer pages before you continue. The waves in a rope moved from side to side are called transverse waves. Transverse means in a crosswise direction. The rope moves across the direction the waves travel. As you move the rope from side to side the waves travel away from you, the source of the waves. Activity: Making waves in a slinky spring This activity requires a slinky spring. (Any coiled spring that you can compress, or squeeze together, with your fingers will do.) If you cannot get a suitable spring read through the activity then do step 3. What you will need: a slinky spring What to do: 1 Lie the slinky in a straight line. It will look like this: 2 Squeeze together the first few rings. Then let the rings go. What do you observe? The energy you put into the spring when you compressed the rings is carried along the spring as a wave. 18 Waves

21 3 Here is a problem you can do, even if you do not have a slinky. The diagram below shows a spring with a compression, or place where it is compressed. The next three diagrams show the wave moving along the spring but the diagrams are not in the correct order. Number them in sequence from 2 to 4. 1 The wave moves from right to left, so the numbers are 1, 2, 4 and 3. The waves in the spring moved along the direction that the waves travel. Waves which move along the direction that the waves travel are called longitudinal waves. Water waves If you ve been in a boat on waves, then you know the feel of waves going up and down. They make a pattern like the pattern of waves in a rope. Ocean water waves produce movement up and down across the direction the waves are travelling. They can be called transverse waves. Part 1 Waves carry energy 19

22 Activity: Drawing water waves from above What you will need: a dish, tray or sink that will hold water an eye-dropper a cup some food colouring or water paint. What to do: 1 Fill the dish with water. Add some food colouring to make the water coloured. The colour makes patterns on top of the water easier to see. Let the water sit until its surface is smooth. 2 Put extra water into the cup and draw some up into the eye dropper. Drop one drop of water into the middle of the tray of water. 3 What do you see? Let the water settle, then add another drop. What pattern forms? Draw the pattern on the sketch below. tray of water drop of water here Did you notice that circles formed around the point where you dropped the water? These circles got bigger and bigger as they moved outwards on the tray. 20 Waves

23 tray of water drop of water here ripples in the water Sound waves Sound waves are easy waves to detect, make and think about. You have your own built-in sound detectors ears and your own sound sources such as your voice box or clapping hands. Similar ways are used to describe or draw the different kinds of waves. So what you learn about sound waves will help you to understand other kinds of waves as well. Learning about other kinds of waves will also help you understand more about sound waves. For example, the diagram you used to show water waves can help you to picture sound waves. tray of water drop of water here ripples in the water Part 1 Waves carry energy 21

24 How is this pattern like sound waves? The drop of water was added to one place. The energy in the push from the drop spreads out in all directions over the water in the tray. In a similar way sound starts in one place, the source, and spreads out in all directions. You can hear someone speaking whether you are in front of them or behind them or even above or below them. Sound energy moves in waves even though we cannot see sound waves moving through matter. When a drawing showing sound waves is made, it often looks like the water waves in the dish above. The lines represent sound energy moving out in waves from the central source. But remember, the sound waves actually travel in three dimensions, not just the two dimensions shown in a drawing. Activity: Different ways of drawing sound waves 1 Draw lines onto the diagram below to show the sound of a dog s bark travelling outwards. The lines in a diagram of sound waves can be replaced by series of dots. 22 Waves

25 The dots in this diagram represent particles in the air. This reminds you that sound is only transmitted through the particles that make up matter. Spaces where particles are drawn close together are compressions, whereas spaces with few particles are rarefactions. A sound wave is sometimes described as a compression wave because it is made up of compressions separated by rarefactions. 2 On the diagram above, label a compression and a rarefaction. Another way of showing compressions and rarefactions uses lines: Label a compression and a rarefaction on the diagram above. 3 Here is a summary to complete about sound waves: Sound energy travels through as sound waves. It travels at speeds in different kinds of matter. sound wave consists of compressions, where are close together, and where particles are widely apart. Sound spreads out all directions from the, where the sound is. Part 1 Waves carry energy 23

26 Please turn to the answer pages to check your diagram and summary. Electromagnetic waves Electromagnetic waves are a group of waves that can be difficult to imagine. They are different from all the waves you have learned about so far, because electromagnetic waves do not need a medium to travel through. Electromagnetic waves can travel though space and through some kinds of matter. Your body has the ability to detect: electromagnetic light waves with eyes electromagnetic infra-red (heat rays) with skin heating up electromagnetic ultraviolet with skin tanning. These waves are called electromagnetic because they are made up of changing electric and magnetic fields. Some examples of electromagnetic waves are light, heat rays, X-rays and radio waves. Activity: Transmitters of electromagnetic waves Think of some substances that the types of electromagnetic waves below can travel though. a b c d light X-rays radio waves heat rays There are some suggestions in the answer pages. 24 Waves

27 When we draw electromagnetic waves, they are usually shown like a wave in a rope, as: Any wave of this shape is called a sine wave. All kinds of electromagnetic waves travel very quickly. Through a vacuum they all travel at metres per second (3 x 10 8 ms 1 ). Like all other waves, electromagnetic waves are a way that energy moves from one place to another. Go to the exercises section and complete Exercise 1.4: Waves as carriers of energy. What did you achieve? Tick what you can do. list different kinds of waves, such as waves in ropes, waves in springs, water waves, electromagnetic waves and sound waves draw or describe different kinds of waves use the concept that waves are carrier of energy. Part 1 Waves carry energy 25

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29 Lesson 5 Describing and visualising waves There are many types of waves sound, water, electromagnetic waves like light as well as earthquake waves covered in your course. Waves can be drawn in a number of ways. Here is a selection: 1 Waves produced by moving a rope up and down direction waveform moves direction of initial vibration rest position of rope 2 Waves close to a source, near the source and far from the source spherical wavefront plane wavefront point source near source far from source Part 1 Waves carry energy 27

30 3 Waves produced by dropping a cork in water cork dropped here Top view Front view 28 Waves

31 4 Wave crests (high points) and troughs (low points) drawn as wavefronts flow of energy wavefronts 5 Waves shown as wavefronts and a ray drawn in the wave direction direction of wave The most common representation of a wave is as a sine curve: wavelength Part 1 Waves carry energy 29

32 The wavelength of the wave is the distance between two consecutive crests (high points), two consecutive troughs (low points) or any two consecutive corresponding points. Corresponding points are points at the same position on the wave. Activity: Measuring wavelength of waves Use a ruler to measure the wavelength of these waves to the nearest millimetre 1 wavelength 2 mm 3 mm mm Check your answers in the answer pages. 30 Waves

33 Compare the two waves in the diagrams below. Use a ruler to confirm that the two diagrams have the same wavelength. However, the two waves differ in their amplitude. Amplitude is the maximum distance from the central position. Check that the crest and trough in the first wave are 18 mm from the central position in the first diagram and 10 mm from the central position in the second diagram. If these diagrams represented waves in ropes the first would require you to move your hand up and down most and would carry the most energy. If sound waves, the first would be louder than the second. The first would carry more energy and move your eardrum the most. If water waves, the first would move more sand on the beach than the second. Oscilloscopes An oscilloscope is a device that helps you visualise waves. You have probably already seen oscilloscopes in hospitals or in movies or on TV. They are used to give a visual image of the beating of a heart, breathing or blood pressure of a patient. First some of the wave energy needs to be changed into electrical energy. Sound wave energy entering a microphone, light energy entering a photoelectric cell and kinetic energy (from movement or pressure) entering a transducer can all send electrical energy to an oscilloscope. You can obtain free software over the Internet that turns your computer into an oscilloscope. Some websites enable you to simulate the operation of a cathode ray oscilloscope (CRO) on your computer screen. Go to < Select Science, then Stage 5 Junior Science and follow the links to resources for this unit, Waves. Part 1 Waves carry energy 31

34 The oscilloscope changes electrical energy into light energy on a small screen. The screen is at the end of a cathode ray tube. The oscilloscope is often called a cathode ray oscilloscope or CRO. (pronounced the same way as the word crow, a type of bird). The pattern of the sound wave s image on the oscilloscope screen is called a wave trace. The wave trace on this oscilloscope screen is an example of a sine wave. Oscilloscope This is the wave trace for a loud sound. And this is the wave trace for a soft sound. Both of these waves have the same wavelength. The sound waves only differ from each other in loudness heard and amplitude seen on the CRO. 32 Waves

35 How is the wave trace of a loud sound different from the wave trace of a soft sound? The loud sound makes a taller wave trace than the soft sound. A more scientific answer would say that the loud sound produces a wave with larger amplitude. Look at the drawing of an oscilloscope screen below. Notice that the screen has a line through the centre of the wave trace. Scientists measure the largest distance that any part of the wave trace can be away from this middle line. Using your ruler, measure the largest distance that the wave trace on this oscilloscope is above the middle line. Measure in millimetres. The largest distance of the wave trace above the middle line is 14 mm. Now measure the largest distance that the wave trace goes below the middle line. The largest distance of the wave trace below the middle line is 14 mm. Here are wave traces of the loud sound and the soft sound that you considered previously. Part 1 Waves carry energy 33

36 Loud sound Soft sound Which sound has more energy? What is the amplitude of the loud sound? What is the amplitude of the soft sound? Which sound has the larger amplitude? The loud sound has more energy. The loud sound has the larger amplitude (19 mm). The soft sound has less energy and a smaller amplitude (10 mm). How can you tell the amount of energy in a sound from its wave trace? The amplitude of a wave trace gives you information about the amount of energy. A sound with lots of energy has a larger amplitude whereas a sound with a smaller amount of energy has a smaller amplitude. 34 Waves

37 Activity: Interpreting amplitude on a CRO Here are the wave traces for three sounds, all with the same wavelength. a b c 1 What is the amplitude of wave trace a? 2 What is the amplitude of wave trace b? 3 What is the amplitude of wave trace c? 4 Which sound has the smallest amplitude? 5 Which sound has the most loudness? 6 Which sound has the least energy? Check your answers in the answer pages. Go to the exercises section and complete Exercise 1.5: Comparing CRO wave traces. Part 1 Waves carry energy 35

38 What did you achieve? Tick what you can do. identify different ways of drawing waves describe how a CRO helps you visualise amplitude and wavelength of a wave. 36 Waves

39 Suggested answers Part 1 Check your responses against these suggested answers. Activity: Pretest 1 b 2 a 3 d 4 b 5 They are all types of energy! 6 The answers, in order, are electrical, light, sound and heat. Activity: Observations and inferences 1 an orchestra tuning up 2 a heart beat (of a baby) 3 a door bell 4 eating breakfast cereal 5 a car starting and driving off 6 a gong 7 kids on a roller coaster 8 jumping into a pool 9 a basketball game 10 pigs 11 seagulls 12 brushing teeth 13 an electric typewriter 14 a zipper going up and down 15 turkeys! Part 1 Waves carry energy 37

40 Activity: How many people can you hear? There were actually ten people laughing! Did you think that there were that many different voices? Activity: Making waves in a rope 3 4 The energy came from the kinetic energy of your hand. (This kinetic energy came from chemical energy stored in your muscles. That chemical energy came from chemical energy in food which was formed from light energy by photosynthesis in plants. That light energy came from nuclear energy in the Sun). 5 A single wave bump moves along the rope. It looks the same and travels at the same speed all the way along the rope. Activity: Different ways of drawing sound waves 1 Remember sound spreads out in all directions from the dog. compression rarefaction 38 Waves

41 2 compression rarefaction 3 Your summary below may not have exactly the same words, but it should have the same meaning. Sound energy travels through matter as sound waves. It travels at different speeds in different kinds of matter. A sound wave consists of compressions, where particles are close together, and rarefactions where particles are spaced widely apart. Sound spreads out in all directions from the source, where the sound is made. Activity: Transmitters of electromagnetic waves a b c d air, water, glass, transparent materials, vacuum human body, luggage at airports, most materials air, water, vacuum of space, non-metallic materials air, water, vacuum of space. Activity: Measuring wavelength of waves Your answers should be the same as or differ by only 1 mm from the answers below: 1 16 mm 2 10 mm 3 26 mm. Activity: Interpreting amplitude on a CRO 1 21 mm 2 28 mm 3 15 mm 4 c 5 b 6 c Part 1 Waves carry energy 39

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43 Exercises Part 1 Exercises 1.1 to 1.5 Name Teacher Exercise 1.1 Revision of energy concepts 1 Distinguish between matter and energy. 2 Distinguish between energy transformation and energy transfer. 3 Explain why the idea of conservation of energy is called a law in science. Part 1 Waves carry energy 41

44 Exercise 1.2 Labelling parts involved in human hearing 1 Label the auditory canal, ear and eardrum of the outer ear: 2 Label the stirrup bone (smallest bone in the human body) of the middle ear, cochlea of the inner ear and the auditory nerve connected to the brain. 42 Waves

45 Exercise 1.3 Vibrations and sound 1 Why is sound considered a type of energy? 2 What evidence is there that sound is produced by vibrations? 3 Use a rubber band to demonstrate that vibration can produce sound waves. Write sentences to outline (that is, indicate the main features of) the activity you perform. The sentences can be arranged as numbered steps like this: or as bullet points like this: Try to write a clear outline so that another person of your age, given a rubber band and your outline, could also perform the activity. Part 1 Waves carry energy 43

46 Exercise 1.4 Waves as carriers of energy 1 An earthquake in South America can produce waves in Sydney Harbour. Explain how the energy from the earthquake is transferred to Sydney Harbour. 2 A storm with strong winds near New Zealand can produce three or four metre waves on the east coast of Australia. Explain how the energy is transferred from New Zealand to Australia. 3 The energy that keeps you alive and moving originally came from the Sun. Explain how waves carried this energy that keeps you alive on Earth from the Sun. 4 Explain how nuclear energy released in the Sun enables you to make sound waves with your voice box. 44 Waves

47 Exercise 1.5 Comparing CRO wave traces Here are the wave traces for four sounds that are travelling through water. H I J K 1 What is the amplitude of sound H? 2 Which sounds have the same loudness? 3 Which sounds have the same wavelength? 4 What is the wavelength of sound H? 5 Which sound has the lowest frequency? 6 Which sounds have the same frequency? 7 Compare sound H with sound I. 8 Compare sound I with sound J. Part 1 Waves carry energy 45

48 9 Could you draw a sound wave without an amplitude? Why or why not? 10 Sketch a wave trace for a sound that is softer and higher than sound J. (A pale outline of sound J is provided to help you.) 46 Waves