Sound Waves - PDF Practice Questions and Answers

3.1, 3.2 & 3.3, 13.1, 13.2, 13.3 & 13.4 Sound Waves 1 Types of wave (Recap) 2 Waves Waves are a way of transferring energy from place to place. 3 4 5 Waves...

3.1, 3.2 & 3.3, 13.1, 13.2, 13.3 & 13.4 Sound Waves 1 Types of wave (Recap) 2 Waves Waves are a way of transferring energy from place to place. 3 4 5 Waves 6 Waves Transverse waves Particles vibrate in a direction perpendicular to the direction of the wave. e.g. light waves Longitudinal waves Particles vibrate in a direction parallel to the direction of the wave e.g. sound waves 7 Sound waves require medium to travel. 8 What can a sound wave travel through? Sound waves need a medium to travel. Sound cannot travel in vacuum. If the medium changes, the speed of sound changes. Average speed of sound in air = 330 m/s Sound moves fastest through solids and the slowest through gases. Solid à Liquids à Gases 9 Sound moves the fastest through hot air and the slowest through cold air. Characteristics of sound waves 10 Describing sound waves 11 Describing sound waves Amplitude (A) Crest The distance from the centre of the wave to the hightest or lowest point How far from the Height equilibrium point the Distance (m) wave has oscillated. How far the wave has travelled from its starting point Wavelength (λ) The distance between the particular Trough point of the wave to the same point on the next wave 12 Describing sound waves f = 1/T Frequency (Hz) The number of waves per Height second Time (s) Time period (T) The time it takes for one wave 13 Describing sound waves Low frequency High frequency The low frequency waves has longer time period. 14 Loudness Vs. Pitch 15 Loudness of sound 16 Loudness of sound Loudness depends on the amplitude of a wave. Higher amplitude sound waves is louder. Lower amplitude sound waves is quieter. 17 Pitch Shrill Deep 18 Pitch of sound 19 Pitch of sound High pitch (Shrill sound) Low pitch (Deep sound) Pitch depends on the frequency of a wave. Higher frequency (lower time period) sound waves has higher pitch. Lower frequency (higher time period) sound waves is lower pitch. 20 Similarities between ear and microphone 21 Detecting sounds (Ear) 3. Tiny bones amplify the 5. Tiny hair convert vibration into electrical vibrations signal. 4. Vibration passes through the liquid in cochlea. 1. Sound wave enters ear canal. 2. Eardrum vibrates 6. Impulses travel the auditory nerve. 22 Detecting sounds (Microphone) 23 Detecting sounds 24 Audible range of sound and ultrasound 25 The audible frequency range is narrower as human gets older. 26 Intensity of sound (Decibel) 27 Intensity of the sound and decibels The intensity of the sound is measured using sound- level meter on a scale called decibel (dB) scale. The sound with a high intensity is louder. 28 Danger of high intensity sound Loud sound can damage your hearing and it can burst the ear drum. The level of danger depends on the intensity of the sound (dB) and the exposure time. 29 Reducing risk of high intensity sound 30 Sound wave interference 31 Interference When the two waves interact, they can add up or cancel out. This is called inference. 32 Constructive Vs. Destructive interference 33 Application of sound interference 34 Echo 35 Sound can reflect When sound hits hard surface, it got reflected off. (Echo) Sound travels slowly so there is a time delay between your shout and the echo. Like law of reflection of light, angle of incidence of the sound wave is equal to the angle of reflection of the sound wave. 36 Echo can be a problem In cinema, echo is useless. Cinema walls and ceilings are covered with soft, sound- absorbing materials to absorb echoes. 37 Application of sound waves A boat detects an echo from the sea bed after 1 second. The speed of sound in water is 1500 m/s. How deep is the sea? Distance = Speed x Time = 1500 x (1/2) = 750 m SONAR = Sound Navigation and Ranging 38 Echolocation Bats find the distance to objects using echolocation. 39 Ultrasound scanning Transducer transmits ultrasound waves into the woman. Ultrasound waves are reflected by the boundaries between soft tissue as well as from hard surfaces such as bone. The transducer detects echo and use the signals to construct 3D images of the baby. 40 1. Which statement about a sound wave is correct? A It can travel through a vacuum. B It travels at a speed of 330m/s in air. C It cannot be reflected. D It is transverse. 2. Which of the following are properties of sound waves? A They can be reflected. B They can be refracted. C They are longitudinal waves. D All of the above. 41 3. Which of the following statements about sound waves is not correct? A The angle of the reflected sound wave is smaller than that of the incident wave. B Sound is passed on by vibrating particles. C Sound can be used to find the depth of the sea-bed using echoes. D Sound is a longitudinal wave. 4. Which of the following statements best describes an echo? A A sound that is refracted through a substance. B A sound that has a large amplitude. C A sound that has been reflected off a surface. D A sound that is heard only in caves. 42 5. Ships use sound waves to help them navigate the sea bed. Which of the following statements is not correct? A Ships use echoes to calculate the depth of the sea. B The speed of sound is faster in air than in water. C This system of using echoes is called sonar. D The sound waves reflect off the bottom of the sea bed. 6. A student is calculating the speed of sound in air. Which of the following equations would she use? A speed = distance × time B speed = distance/time C speed = frequency/wavelength D speed × frequency = wavelength 43 7. A student stands 50 m in front of a building. He claps two blocks together and listens for the echo from the buildings. It takes 5.85 seconds to hear 20 echoes. What is the speed of sound? A 171 m/s B 341 m/s C 1700 m/s D 34 m/s 44 8. The audible range of human hearing is said to range from 20 Hz to 20 000 Hz. What is meant by audible range? A hearing B the range that all animals and humans can hear C the range which a speaker can generate D the range of frequencies which humans can hear 9. The oscilloscope trace shows a number of different sounds. Which sound has the highest pitch? A sound A B sound B C sound C D sound D 45 10. Which of the sound waves will be the loudest? A sound A B sound B C sound C D sound D 11. A whistle produces a sound of frequency 25 000 Hz. Which of the following statements are correct? A Humans would be able to hear the sound. B Elephants and humans would be able to hear the sound. C Dolphins would be able to hear the sound. D Elephants and dogs would be able to hear the sound. 46