Edexcel IGCSE Physics Sound Revision Notes PDF

Head to www.savemyexams.com for more awesome resources Edexcel IGCSE Physics Your notes Sound Contents Core Practical: Investigating the Speed of Sound Sound & Oscilloscopes Core Practical: Using an Oscilloscop...

Head to www.savemyexams.com for more awesome resources Edexcel IGCSE Physics Your notes Sound Contents Core Practical: Investigating the Speed of Sound Sound & Oscilloscopes Core Practical: Using an Oscilloscope Pitch & Loudness Page 1 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Core Practical: Investigating the Speed of Sound Your notes Core practical 6: investigating the speed of sound Equipment Equipment List Equipment Purpose Trundle Wheel To measure the distance travelled by the sound waves Wooden Blocks To create a sound when banged together Stopwatch To time how long it takes the sound waves to travel Oscilloscope To display the sound wave electronically Microphones x2 To detect sound waves and turn them into an electrical signal Tape Measure To measure the distance between microphones Resolution of measuring equipment: Trundle wheel = 0.01 m Tape measure = 0.1 cm Stopwatch = 0.01 s Experiment 1: measuring the speed of sound between two points The aim of this experiment is to measure the speed of sound in air between two points Variables Independent variable = Distance Dependent variable = Time Control variables: Page 2 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Same location to carry out the experiment Method Your notes Measuring the speed of sound in air Measuring the speed of sound directly between two points 1. Use the trundle wheel to measure a distance of 100 m between two people 2. One of the people should have two wooden blocks, which they will bang together above their head to generate sound waves 3. The second person should have a stopwatch which they start when they see the first person banging the blocks together and stop when they hear the sound 4. This should be repeated several times and an average taken for the time travelled by the sound waves 5. Repeat this experiment for various distances, e.g. 120 m, 140 m, 160 m, 180 m Results An example results table for the speed of sound in air Page 3 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Distance / m Time 1 / s Time 2 / s Time 3 / s Average time / s Your notes 100 120 140 160 180 Analysis of results The speed of sound can be calculated using the equation: distance moved average speed = time taken The speed of sound in the air should work out to be about 340 m/s Experiment 2: measuring the speed of sound with oscilloscopes The aim of this experiment is to measure the speed of sound in air between two points using an oscilloscope Variables Independent variable = Distance Dependent variable = Time Control variables: Same location to carry out the experiment Same set of microphones for each trial Method Measuring the speed of sound with an oscilloscope Page 4 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Measuring the speed of sound using an oscilloscope 1. Connect two microphones to an oscilloscope 2. Place them about 2 m apart using a tape measure to measure the distance between them 3. Set up the oscilloscope so that it triggers when the first microphone detects a sound, and adjust the time base so that the sound arriving at both microphones can be seen on the screen 4. Make a large clap using the two wooden blocks next to the first microphone 5. Use the oscilloscope to determine the time at which the clap reaches each microphone and the time difference between them 6. Repeat this experiment for several distances, e.g. 2 m, 2.5 m, 3 m, 3.5 m Results An example results table for obtaining the speed of sound using an oscilloscope Distance / m Time 1 / s Time 2 / s Time 3 / s Average time / s 2.0 Page 5 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources 2.5 Your notes 3.0 3.5 4.0 Analysis of results The speed of sound can be calculated using the equation: distance moved average speed = time taken The speed of sound in the air should work out to be about 340 m/s Evaluating the experiments Systematic Errors: In experiment 2, ensure the scale of the time base is accounted for correctly The scale is likely to be small (e.g. milliseconds) so ensure this is taken into account when calculating speed Random errors: The main cause of error in experiment 1 is the measurement of time Ensure to take repeat readings when timing intervals and calculate an average to keep this error to a minimum Maximise the distance between the two people where possible. This will reduce the error in measurements of time because the time taken by the sound waves to travel will be greater Examiner Tips and Tricks When answering questions about methods to measure waves, the question could ask you to comment on the accuracy of the measurements. In the case of measuring the speed of sound: Page 6 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Experiment 2 is the most accurate because the timing is done automatically Experiment 1 is the least accurate because the time interval is very short Whilst this may not be too important when giving a method, you should be able to explain why each Your notes method is accurate or inaccurate and suggest ways of making them better (use bigger distances) For example, if a manual stopwatch is being used there could be variation in the time measured which can be up to 0.2 seconds due to a person's reaction time The time interval could be as little as 0.3 seconds for sound travelling in the air This means that the variation due to the stopwatch readings has a big influence on the results and they may not be reliable Page 7 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Sound & Oscilloscopes Your notes Sound & oscilloscopes An oscilloscope is a device that can be used to study a rapidly changing signal, such as: A sound wave An alternating current An oscilloscope is used to display sound as a waveform Oscilloscopes have lots of dials and buttons, but their main purpose is to display and measure changing signals like sound waves and alternating current When a microphone is connected to an oscilloscope, the (longitudinal) sound wave is displayed as though it were a transverse wave on the screen The properties of longitudinal and transverse waves are explained in the revision note Transverse & longitudinal waves The time base (like the 'x-axis') is used to measure the time period of the wave An explanation of the sound waveform as displayed on an oscilloscope Page 8 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes A sound wave is displayed as though it were a transverse wave on the screen of the oscilloscope. The time base can be used to measure a full time period of the wave cycle The height of the wave (measured from the centre of the screen) is related to the amplitude of the sound The number of entire waves that appear on the screen is related to the frequency of the wave If the frequency of the sound wave increases, more waves are displayed on screen Examiner Tips and Tricks Take time to understand how the oscilloscope displays sound as a waveform, as it is more complicated than you think. Make sure you know what happens to the wave if you change either the horizontal or vertical axis. Page 9 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Core Practical: Using an Oscilloscope Your notes Core practical 7: using an oscilloscope Aims of the experiment The aim of this experiment is to investigate the frequency of a sound wave using an oscilloscope Variables Independent variable = Tuning forks of different frequencies Dependent variable = Time period Equipment Equipment List Equipment Purpose Tuning fork To generate sound waves of different frequencies Microphone To detect sound waves from the tuning fork Oscilloscope To display the sound waves electronically Wires To connect the microphone to the oscilloscope Method A diagram of the oscilloscope and tuning fork set up Page 10 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Measuring the frequency of a sound wave using an oscilloscope 1. Connect the microphone to the oscilloscope as shown in the image above 2. Test the microphone displays a signal by humming 3. Adjust the time base of the oscilloscope until the signal fits on the screen - ensure that multiple complete waves can be seen 4. Strike the tuning fork on the edge of a hard surface to generate sound waves of a pure frequency 5. Hold the tuning fork near to the microphone and observe the sound wave on the oscilloscope screen 6. Freeze the image on the oscilloscope screen, or take a picture of it 7. Measure and record the time period of the wave signal on the screen by counting the number of divisions for one complete wave cycle 8. Repeat steps 4-6 for a variety of tuning forks Results An example results table of the oscilloscope display Page 11 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Analysis of results To convert the time period of the wave from the number of divisions into seconds, use the scale of the time base. For example: The time base is usually measured in units of ms/cm (milliseconds per centimetre) This would mean a wave with a time base of 4 cm has a time period of 4 ms To calculate the frequency of the sound waves produced by the tuning forks, use the equation: 1 f = T This is explained in more detail in the revision note The wave equation Evaluating the experiment Systematic Errors: Ensure the scale of the time base is accounted for correctly The scale is likely to be small (e.g. milliseconds) so ensure this is taken into account when calculating the time period Random Errors: Page 12 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources A cause of random error in this experiment is noise in the environment, so ensure it is carried out in a quiet location Your notes Examiner Tips and Tricks You have a lot of core practicals to know about. Make sure you don't get those relating to sound confused with each other. To succeed in questions about this particular practical you need to know exactly how an oscilloscope works. To do that revise this in the revision note about Sound & oscilloscopes. Page 13 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Pitch & Loudness Your notes Pitch The pitch of a sound is related to the frequency of the vibrating source of sound waves If the frequency of vibration is high, the sound wave has a high pitch If the frequency of vibration is low, the sound wave has a low pitch The relationship between the pitch and frequency of sound The pitch of the sound is related to the frequency of the sound waves Comparing the pitch of sound displayed on an oscilloscope Page 14 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes This image shows two sound waves displayed on an oscilloscope. The red wave has smaller wavelength than the blue wave hence it has higher frequency and higher pitch Loudness The loudness of a sound is related to the amplitude of the vibrating source of sound waves If the sound is loud, the sound wave has a large amplitude Comparing the volume of sound displayed on an oscilloscope Page 15 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes This image shows two sound waves displayed on an oscilloscope. The blue wave has twice the amplitude of the green wave because the blue wave is louder Range of human hearing The human ear responds to the vibrations caused by sound waves The frequency range for human hearing is 20 Hz to 20 000 Hz Below the frequencies that humans can hear is infrasound Above the frequencies that humans can hear is ultrasound The infrasound, human hearing and ultrasound frequency ranges Page 16 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes The range of human hearing is between 20 – 20 000 Hz. Below 20 Hz is known as infrasound. Above 20 000 Hz is known as ultrasound Examiner Tips and Tricks Remember that altering the frequency of a sound wave does not affect the volume, only the wave pitch. Changing the amplitude of the wave changes the volume. Page 17 of 17 © 2015-2025 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers