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4 Waves G482 Electricity, Waves & Photons 4 Waves G482 Electricity, Waves & Photons 2.4.1 Wave Motion 2.4.1 Wave Motion Mr Powell 2012 Index 2.4.2. EM.

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Presentation on theme: "4 Waves G482 Electricity, Waves & Photons 4 Waves G482 Electricity, Waves & Photons 2.4.1 Wave Motion 2.4.1 Wave Motion Mr Powell 2012 Index 2.4.2. EM."— Presentation transcript:

1 4 Waves G482 Electricity, Waves & Photons 4 Waves G482 Electricity, Waves & Photons Wave Motion Wave Motion Mr Powell 2012 Index EM Waves EM Waves Interference Interference Stationary Waves Stationary Waves

2 Mr Powell 2012 Index Practical Skills are assessed using OCR set tasks. The practical work suggested below may be carried out as part of skill development. Centres are not required to carry out all of these experiments. Students should gain a qualitative understanding of superposition effects together with confidence in handling experimental data. Students should be able to discuss superposition effects and perform experiments leading to measurements of wavelength and wave velocity. Study hearing superposition using a signal generator and two loudspeakers. Demonstrate stationary waves using a slinky spring, tubes and microwaves. Determine the speed of sound in air by formation of stationary waves in a resonance tube.

3 Mr Powell 2012 Index Stationary Waves 4 – Air Columns Assessable learning outcomes.... (d) describe experiments to demonstrate stationary waves using air columns; (p160) (e) determine the standing wave patterns for air columns in closed and open pipes; (p162) (h) determine the speed of sound in air from measurements on stationary waves in a pipe closed at one end. (p163) Assessable learning outcomes.... (d) describe experiments to demonstrate stationary waves using air columns; (p160) (e) determine the standing wave patterns for air columns in closed and open pipes; (p162) (h) determine the speed of sound in air from measurements on stationary waves in a pipe closed at one end. (p163)

4 Mr Powell 2012 Index Strings reminder Must be fixed as it is a string!

5 Mr Powell 2012 Index The closed tube must have a node or lack of motion at an end. (displacement model) Particles must get stuck here (stopped) Pressure is always low at the open end. Stationary Waves in Tubes.... The open tube will have max movement (amplitude) of particles at both ends with antinodes. Musical instruments have two open ends but reflection does still occur & resonance. Pressure must be low or room pressure at the end of the tube or antinode. Motion Pressure Change Node LowHigh AntinodeHighLow TASK: Write your own version in your own words! Use the book to help and the next slide as well!

6 Mr Powell 2012 Index Displacement Model....

7 Mr Powell 2012 Index Why are nodes formed in fixed positions? Finding the Speed of Sound Experiment… You have the equipment shown in the diagram and also a selection of tuning forks and tube sizes. Record your results in a suitable table and see if you can work out the speed of sound…. Ensure you quote any errors (converting to an overall error) and write a conclusion about your results.

8 Mr Powell 2012 Index Speed of Sound – Extra Help… Frequency (Hz) Length (m)Wavelength (m) Velocity (ms -1 ) Ave 343 dry air 20 o C You might use a table as shown below… Also you might decide to repeat your readings for more accuracy. Conclusions might talk about what happens to the velocity of the various waves? 343 dry air 20 o C /4 5 /2 3 /2 Max amp at end

9 Mr Powell 2012 Index Speed of Sound – Extra Help… Frequency (Hz) Length (m)Wavelength (m) Velocity (ms -1 ) Ave dry air 20 o C You might use a table as shown below… Also you might decide to repeat your readings for more accuracy. Conclusions might talk about what happens to the velocity of the various waves? /4 5 /2 3 /2 Max amp at end

10 Mr Powell 2012 Index Oscillating an Air Column? Legnth tube /mInternal DiameterFrequencynWavelengthVelocity Speed of Sound in Air In dry air at 20 °C the speed of sound is m/s Lab Temp22.7 Corrected for Tube Diam f = nc/n(L+0.3d) c = f * lambda Theoretical Temperture Adjusted Velocity of Sound in Air 345 2(L+0.3d)/n = lambda % Diff5 v = 331.5m/s + 0.6T v = velocity of sound at that temp T = temperature (°C)

11 Mr Powell 2012 Index Oscillating an Air Column?

12 Mr Powell 2012 Index Data Trends... (Extension) Discuss this data with a partner. Can you see a trend in the numbers? Can you comment on... Gas -> Liquid -> Solid the mass of the molecules or compounds? (as best you know) Ethanol C 2 H 5 OH Chloroform CHCl 3 Glass SiO 2 The bonding or strength of the structures You can use the periodic table to help you? Think helium and voice box (fixed )

13 Mr Powell 2012 Index Revision/ Extension… Visit the sites show below and then write a paragraph and numerical example for each. Inverse square law calculation: Geological example of sound reflection: Pitch: Loudness of wave: String properties: Wave properties and more :

14 Mr Powell 2012 Index Typical Exam Question (ii)When the fundamental wave is heard, the length of the air column is 0.32 m. Determine the wavelength of the standing wave formed. wavelength = m [1] (iii)The speed of sound in air is 330 m s–1. Calculate the frequency of the tuning fork. frequency = Hz [3] [Total 6 marks] 1.The figure below shows a long glass tube within which standing waves can be set up. A vibrating tuning fork is placed above the glass tube and the length of the air column is adjusted, by raising or lowering the tube in the water, until a loud sound is heard. (i)The standing wave formed in the air column is the fundamental (the lowest frequency). Show on the figure the position of a node – label as N, and an antinode – label as A. [2]

15 Mr Powell 2012 Index Typical Exam Question

16 Mr Powell 2012 Index Connection Connect your learning to the content of the lesson Share the process by which the learning will actually take place Explore the outcomes of the learning, emphasising why this will be beneficial for the learner Connection Connect your learning to the content of the lesson Share the process by which the learning will actually take place Explore the outcomes of the learning, emphasising why this will be beneficial for the learner Demonstration Use formative feedback – Assessment for Learning Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex Offer different ways for the students to demonstrate their understanding Allow the students to show off their learning Demonstration Use formative feedback – Assessment for Learning Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex Offer different ways for the students to demonstrate their understanding Allow the students to show off their learning Activation Construct problem-solving challenges for the students Use a multi-sensory approach – VAK Promote a language of learning to enable the students to talk about their progress or obstacles to it Learning as an active process, so the students arent passive receptors Activation Construct problem-solving challenges for the students Use a multi-sensory approach – VAK Promote a language of learning to enable the students to talk about their progress or obstacles to it Learning as an active process, so the students arent passive receptors Consolidation Structure active reflection on the lesson content and the process of learning Seek transfer between subjects Review the learning from this lesson and preview the learning for the next Promote ways in which the students will remember A news broadcast approach to learning Consolidation Structure active reflection on the lesson content and the process of learning Seek transfer between subjects Review the learning from this lesson and preview the learning for the next Promote ways in which the students will remember A news broadcast approach to learning

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20 Mr Powell 2012 Index In a stationary wave all the particles in a between a node are acting in phase.. i.e. they travel up at the same time. In a progressive wave each part of the wave is out of phase as you move along the wave through 360 ……. Q3

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