unit 14 – waves (student’s book, pp. 305–312) · unit 14 – waves (student’s book, pp....

3
Teacher’s Handbook Unit 14 – Waves (Student’s Book, pp. 305–312) © Smart Learning Ltd 2014 – For use by purchasing institution only. Unit introduction Units 10 and 11 introduce students to sound and the behaviour of sound waves, while Units 12 and 13 focus on light and the behaviour of light waves. Unit 14 brings together those ideas in order to explain the more theoretical topic of waves generally. The essential points to cover are: water waves can be investigated as a model for all transverse waves including light; sound waves are longitudinal; all waves exhibit some similar behaviour, including carrying energy and/or information. Coverage NC 2014 KS3: P9.1 Transverse waves on water, including their reflection and superposition. NC 2014 KS3: P11.1 Waves as carriers of energy and information, with uses (cleaning by ultrasound and audio recording). NC 2014 KS3: P12.1 The similarities and differences between light waves and waves in matter. NC 2014 KS3: P12.5 Light waves as a means of transferring energy, including within the eye and in cameras. Prior knowledge Physics Unit 11: Sound waves travel through the air from a vibrating source (Student’s Book, page 288). Physics Unit 12: Light can travel through empty space (Student’s Book, page 295). Data handling Drawing accurate diagrams of transverse waves, showing wavelength and amplitude. Measuring time taken and distance travelled by a water wave in a ripple tank, to calculate speed. Superimposing two waves on diagrams to show how they can add up or cancel out. Contexts Examples of observable waves in the real world, including on the oceans and in the form of light. Examples of sound waves passing through each other, including hearing all the different instruments in an orchestra. Hearing and sight as examples of the transfer of information by waves. Earthquakes as examples of the transfer of energy by waves. Related resources Four Structured Questions ss_sq_phys_14_waves_qs and marking guide ss_sq_phys_14_waves_mg. Controlled Assessments ‘Watching wavesss_ca_phys_14_waves_si and ss_ca_phys_14_waves_tg. End of unit test ‘Waves’ ss_et_phys_14_waves_qs and ss_et_phys_14_waves_mg. Progression ALL students should (levels 3–4): Understand that transverse waves can be shown using water in a ripple tank. Recall that the wavelength of a wave is the distance from one wave crest to the next. Know that water waves and light are examples of transverse waves; sound waves are examples of longitudinal waves. Recall that waves can pass through each other, and can transfer energy or information from place to place. MOST students should (levels 5–6): Explain the difference between transverse waves and longitudinal waves. Describe how a ripple tank or two torch beams can be used to show waves passing through each other. Describe what happens when waves meet, including how they can add together or cancel out. Explain that the particles of water in a water wave do not move along, they only move up and down. Describe how a long spring can be used to demonstrate transverse and longitudinal waves. SOME students will (levels 6–7): Explain how a wave is a travelling disturbance of particles, and describe some of the possible causes of tsunamis. Describe an investigation using a ripple tank to calculate the speed at which a wave travels. Explain what happens to a water wave reflected at an angle, using a diagram. Draw diagrams showing how two waves can add up or cancel each other out. Describe and explain examples of waves carrying information and energy.

Upload: lytram

Post on 07-Sep-2018

222 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Unit 14 – Waves (Student’s Book, pp. 305–312) · Unit 14 – Waves (Student’s Book, pp. 305–312) !! ... Physics Unit 11: ... The questions get progressively more challenging

Teac

her’s

Han

dboo

k

Unit 14 – Waves

(Student’s Book, pp. 305–312)  

  © Smart Learning Ltd 2014 – For use by purchasing institution only.

Unit introduction Units 10 and 11 introduce students to sound and the behaviour of sound waves, while Units 12 and 13 focus on light and the behaviour of light waves. Unit 14 brings together those ideas in order to explain the more theoretical topic of waves generally. The essential points to cover are: water waves can be investigated as a model for all transverse waves including light; sound waves are longitudinal; all waves exhibit some similar behaviour, including carrying energy and/or information.

Coverage

NC 2014 KS3: P9.1 Transverse waves on water, including their reflection and superposition. NC 2014 KS3: P11.1 Waves as carriers of energy and information, with uses (cleaning by ultrasound and audio recording). NC 2014 KS3: P12.1 The similarities and differences between light waves and waves in matter. NC 2014 KS3: P12.5 Light waves as a means of transferring energy, including within the eye and in cameras.

Prior knowledge

Physics Unit 11: Sound waves travel through the air from a vibrating source (Student’s Book, page 288). Physics Unit 12: Light can travel through empty space (Student’s Book, page 295).

Data handling

Drawing accurate diagrams of transverse waves, showing wavelength and amplitude. Measuring time taken and distance travelled by a water wave in a ripple tank, to calculate speed. Superimposing two waves on diagrams to show how they can add up or cancel out.

Contexts

Examples of observable waves in the real world, including on the oceans and in the form of light. Examples of sound waves passing through each other, including hearing all the different instruments in an orchestra. Hearing and sight as examples of the transfer of information by waves. Earthquakes as examples of the transfer of energy by waves.

Related resources

Four Structured Questions ss_sq_phys_14_waves_qs and marking guide ss_sq_phys_14_waves_mg. Controlled Assessments ‘Watching waves’ ss_ca_phys_14_waves_si and ss_ca_phys_14_waves_tg. End of unit test ‘Waves’ ss_et_phys_14_waves_qs and ss_et_phys_14_waves_mg.

Progression

ALL students should (levels 3–4): • Understand that transverse waves can be shown using water in a ripple tank. • Recall that the wavelength of a wave is the distance from one wave crest to the next. • Know that water waves and light are examples of transverse waves; sound waves are examples of longitudinal waves. • Recall that waves can pass through each other, and can transfer energy or information from place to place.

MOST students should (levels 5–6): • Explain the difference between transverse waves and longitudinal waves. • Describe how a ripple tank or two torch beams can be used to show waves passing through each other. • Describe what happens when waves meet, including how they can add together or cancel out. • Explain that the particles of water in a water wave do not move along, they only move up and down. • Describe how a long spring can be used to demonstrate transverse and longitudinal waves.

SOME students will (levels 6–7): • Explain how a wave is a travelling disturbance of particles, and describe some of the possible causes of tsunamis. • Describe an investigation using a ripple tank to calculate the speed at which a wave travels. • Explain what happens to a water wave reflected at an angle, using a diagram. • Draw diagrams showing how two waves can add up or cancel each other out. • Describe and explain examples of waves carrying information and energy.

Page 2: Unit 14 – Waves (Student’s Book, pp. 305–312) · Unit 14 – Waves (Student’s Book, pp. 305–312) !! ... Physics Unit 11: ... The questions get progressively more challenging

Teac

her’s

Han

dboo

k

Unit 14 – Waves

(Student’s Book, pp. 305–312)  

  © Smart Learning Ltd 2014 – For use by purchasing institution only.

Le

Lesson 2: Investigating water waves Lesson objective: To observe and describe parallel water waves and how they are reflected. Summary: Students work in pairs or small groups to set up and use a ripple tank to produce transverse waves on water. They measure the wavelength of the transverse waves and demonstrate reflection. Coverage: NC 2014 KS3: P9.1 Transverse waves on water, including their reflection and superposition. Resources: Student’s Book page 307 (How can we investigate waves; How can we show that water waves reflect?). Practicals and investigations: ‘Watching waves’ ss_pi_phys_14_waves_si and ss_pi_phys_14_waves_tg. Preparation Ideally each group of four or five students should be able to set up their own ripple tank. If resources are limited, this can be carried out as a demonstration, but ensure students discuss each stage of the investigation in their groups. For detailed instructions and safety notes, see ‘Watching waves’ ss_pi_phys_14_waves_tg. Starter (5 mins) • Check that students recall that water waves are transverse and can label a diagram with crests, troughs and the wavelength.

Ask students to label a diagram on the whiteboard, or to work in small groups to draw their own diagrams. • Ask the class to describe how a boat moves when it is adrift on open water. It is important to ensure everyone grasps the

idea that the boat only moves up and down, and is not moved along sideway (see Student’s Book page 306). Main (50–80 mins) • Divide the class into small mixed ability groups around each ripple tank. Remind them to check their apparatus before they

set it up, and to ensure the drain hole is plugged. Tanks should be set on a level, hard surface away from electrical outlets. • Before students start assembling the apparatus, encourage them to suggest headings for a risk assessment and identify the

main safety precautions. You can support low ability students by drawing up a numbered/prioritised list on the board. • Ask students to follow the instructions ‘Setting up the ripple tank’ (in ‘Watching waves’ ss_pi_phys_14_waves_si). Some

groups may need help, as the arrangement of the clamps and motor with vibrating bar can be tricky. All groups should get their tank reasonably level, half-filled with water and stable. Observe how students place the bar into or on the water – remind them that to produce transverse waves, the bar needs to be placed on the surface of the water not deep in it.

• Check each group’s apparatus is set up correctly and safely. It may be necessary to dim the classroom lights and/or cover windows to observe the shadows of the waves clearly. Challenge students to think about which parts of the apparatus can be changed (position of light, height of tank, height of vibrating bar) and to adjust these one at a time to observe the results.

• Now ask groups to switch on the motor and make adjustments to produce a clear picture of the wave shadows. Students should sketch the wave patterns they observe. Check: Can they see the wave shadows clearly? If not, get groups to compare their apparatus set-up with another group’s. If students struggle with drawing clearly, they can work in groups to trace the shadows on the main paper underneath the tank. Encourage more able students to measure the wavelength; time allowing they could adjust the motor speed, record the effects on the waves and wavelengths, and calculate wave speed.

• Reflection: groups insert a solid bar at the opposite end of the tank from the vibrating bar but parallel to it, and observe the outcome. More able students measure the wavelength of incident and reflected waves (all students can try this later).

• Angled reflection: if time allows, ask student groups to angle the stationary bar and draw the resulting wave patterns. Plenary (5 mins) Ask a spokesperson from each group what they discovered about water waves and how they are reflected. Challenge more able students to describe what happened when the frequency of the vibrating bar changed. If some groups struggled to make clear observations, ask them to write down what they think should occur then compare their predictions with successful groups. Literacy opportunities Talk and teamwork: Use the stages of setting up and adjusting the apparatus to prompt clear expression and active listening. Students then produce a step-by-step verbal description of the tasks with others intervening to correct or provide clarification. Report writing: Use the plenary session or homework to develop students’ report-writing skills (see Homework below). Numeracy opportunities Measuring wavelength and observing the effects on wavelength of adjusting the frequency of the vibrating bar. More able students can use the equation speed = distance/time taken to estimate the speed of incident and reflected waves. Homework Main: Students write up the investigation, including a hypothesis, diagrams of apparatus and results, and conclusion. Lower ability students can focus on the ‘method’ section, recalling the investigation steps and writing them in a numbered sequence. Alternative: Students complete Structured Question 1 from ss_sq_phys_14_waves_qs.doc on water waves and their similarities and differences to light and sound waves. Progress check points ALL students should (levels 3–4): understand that transverse waves can be shown using water in a ripple tank; recall that the wavelength of a wave is the distance from one wave crest to the next; engage in a risk assessment. MOST students should (levels 5–6): describe how what is observed represents transverse waves; correctly set up and adjust ripple tank apparatus to observe waves clearly; write a clear report with correct headings. SOME students will (levels 6–7): describe an investigation using a ripple tank to calculate wave speed; explain what happens to a water wave reflected at an angle, using a diagram; describe how wavelength is not changed by reflection.

Page 3: Unit 14 – Waves (Student’s Book, pp. 305–312) · Unit 14 – Waves (Student’s Book, pp. 305–312) !! ... Physics Unit 11: ... The questions get progressively more challenging

Teac

her’s

Han

dboo

k

Unit 14 – Waves

(Student’s Book, pp. 305–312)  

  © Smart Learning Ltd 2014 – For use by purchasing institution only.

End-of-unit summary End-of-unit test (‘Waves’ ss_et_phys_14_waves_qs and ss_et_phys_14_waves_mg) Warm-up: students complete a wave diagram labelling activity that encourages them to think about key words they will need in some of the main test answers. [5 marks] Main test questions: There are 15 questions in total, three per level from levels 3 to 7, using the old National Curriculum levels as a benchmark. The questions get progressively more challenging in terms of thinking skills, following Bloom’s taxonomy in testing recall, then description and understanding, through explanation and application to eventually test prediction and synthesis of knowledge. The accompanying marking guide illustrates how students may demonstrate their progression in their answers. [26 marks] Six-mark question: Each six-mark question is designed to fit the GCSE model while testing Key Stage 3 knowledge and skills. The marking guide flags typical student statements that demonstrate scientific knowledge and application of that knowledge appropriate to different levels of ability. The marking guide also draws attention to the need for correct spelling, punctuation and grammar in order to gain full marks. [6 marks] The ‘Waves’ six-mark question tests knowledge of transverse waves compared to longitudinal waves. What to do if… Some students may struggle to synthesise their more practical knowledge of the different types of waves (from Units 10 to 13) with the more theoretical and abstract models of waves presented in Unit 14. To support struggling students you could:

• Revisit the conclusions to Unit 11: How sound travels (see Student’s Book pages 288 and 289) in conjunction with the conclusions to Unit 12: Light (see Student’s Book pages 294 and 295).

• Carry out hands-on practical activities or demonstrations of sound forming wave crests and troughs, and sound being reflected (e.g. using a wave generator and oscilloscope, or bouncing sounds round corners). Combine this approach with simple light reflection activities (such as using torches and mirrors) to act as valuable reinforcement.

• Undertake a demonstration or hands-on practical of the slinky spring forming transverse and longitudinal waves, combined with students drawing the wave patterns.

Thinking beyond… To stretch your more able students you could:

• Challenge students to design a water-wave powered machine or generator that works using the up-and-down wave movement. (Some advanced knowledge of dynamos may be required; see the Thinking beyond… for Unit 6: Magnets and Unit 8: Electric current.)

• Ask students to write a report on the uses of sound waves in unusual situations, such as using ultrasound to clean medical equipment, as a focused beam to control crowds of people or to lift objects into the air.

Moving on from this unit Unit 15: Energy resources and Unit 16: Heat develop the themes of energy and energy transfer and can be linked back to Unit 14 in terms of energy transfer by waves. Unit 21: Astronomy offers a further opportunity to discuss waves, in particular light waves and radio waves, in the context of astronomy. Moving on to GCSE This unit leads into the Key Stage 4 National Curriculum by developing qualitative and quantitative explanations in the areas of: Energy:

• Analyse a system before and after a change, and identify the ways in which energy in the system is re-distributed in: movement; vibration.

Waves in matter: • Describe wave motion in terms of the wavelength and frequency of waves in water, explaining how these may be measured,

that they are transverse, that it is the wave and not the water itself that travels; explain the relationship between velocity, frequency and wavelength.

• Compare water waves and sound waves and explain the difference between transverse and longitudinal waves. • Describe and explain superposition in water waves and the effects of reflection, transmission, and absorption of waves at

material interfaces. • Explain, in qualitative terms, how the differences in velocity, absorption and reflection between different types of waves in

solids and liquids can be used to for detection and for exploration of structures which are hidden from direct observation, notably in the Earth’s core and in the oceans.

Quick checks at the end of Unit 14 to test preparedness for GCSE ü Ask students to summarise the differences between transverse and longitudinal waves, and encourage them to give

examples and applications. ü Introduce the terms superposition and transmission. ü Encourage quantitative work based on comparing changes in wavelength and frequency. ü Note that the application of waves in water as a means of detecting hidden structures is included; more able students

towards the end of their Key Stage 3 studies could conduct research into these applications.