Grade 8: Revision pack on
Sound
(A) Write the scientific term for the following sentences: 1. A disturbance that transfers energy from place to place. (________________) 2. The material through which a wave travels. (________________) 3. A repeated back and forth or up and down motion. (________________) or(__________________) 4. Waves that move the medium at right angles to the direction in which the waves are travelling. (__________________________) 5. Waves that move the medium in the same direction in which the waves are travelling. (__________________________) 6. The highest parts of a transversal wave. (________________) 7. The lowest parts of a transversal wave. (________________) 8. The height of a crest above the average water level or the depth of a trough below it. (________________) 9. The part in a longitudinal wave where the particles are close together. (________________) 10. The part in a longitudinal wave where the particles are away from each other.(________________) 11. Reflection of sound waves. (________________) 12. A very high frequency sound that we cannot hear and used in sonar system. (________________) (B) Put (True) or (False): 1. A medium can be a gas, liquid, or solid. ( ______) 2. All waves require a medium to travel through. ( ______) 3. Sound travels faster in a gas than in a liquid, and faster in a liquid than a solid. ( ______) 4. The denser the medium, the faster the sound will travel. ( ______) 5. If the frequency is increased, the pitch of the sound becomes higher. ( ______) 6. If the amplitude is increased, the sound becomes quieter. ( ______) 7. A wave with larger amplitude contains less energy. ( ______) 8. Sound is faster than light. ( ______) (C) Complete the following sentences: 1. Speed = ……………………………../………………………… 2. The pitch of a sound wave is directly related to………………………. and inversely related to ………………………………………. 3. The loudness depends on the ……………………………… of the wave. 4. Quality depends on the………………………………. 5. Sound is measured in …………………. (………..), using a……………………………….. 6. Sound is caused due to ………………………………. 7. Sound is a …………………………. wave. 8. The range of frequencies that a normal human ear can detect is ……………..Hz to……………………….. Hz (D) Give reason(s) for: 1. The higher the temperature, the faster sound will travel. ..............................................................................................................................................
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......................................................................................................... 2. Ultrasonic waves are used in sonar systems instead of audible sound waves. ..............................................................................................................................................
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......................................................................................................... 3. Sound cannot travel though a vacuum. ..............................................................................................................................................
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......................................................................................................... 4. It is possible to hear round corners. ..............................................................................................................................................
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......................................................................................................... (E) Choose the correct answer: 1. Which of the following is a characteristic of sound waves? (a) A medium is necessary for the waves to travel. (b) The waves are transverse. (c) Different types can be compared on the electromagnetic spectrum. (d) They travel faster than other waves 2. What happens to a wave when it is reflected? (a) The wave passes through a medium. (b) The wave is radiated. (c) The wave is transmitted. (d) The wave bounces back after hitting a barrier. 3. How is sound energy carried away from a drum? (a) by a transverse wave (b) by a longitudinal wave (c) by a perpendicular wave (d) by a surface wave (F) Solve the following problems: 1. A laser beam of light can be bounced off the Moon (from a special mirror left there by astronauts). The light travels there and back in 2.6 seconds. What is the distance to the Moon? (Speed of light =3×108 m/s.) ..............................................................................................................................................
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......................................................................................................... 2. Jack is having an ultrasound scan to locate a kidney stone. The probe receives two reflections: one from Jack’s skin and another from the stone. The second reflection is received 0.0001 seconds after the first. The speed of ultrasound waves in human tissue is 1500 m/s. How far was the kidney stone beneath Jack’s skin? …………………………………………………………………………………………………………………………………………
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………………………………………………………………………………………………. 3. A short pulse of sound waves is emitted from a boat, and an echo from a shoal of fish is detected 0.1s later. The sound waves travel through sea‐water at 1500 m/s. a) How far has the pulse travelled in 0.1 s? ………………………………………………………………………………………………………………...………………………
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……………………………………………………………………………...……………… b) How far below the boat is the shoal of fish? …………………………………………………………………………………………………………………………………………
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…………………………………………………………….. (G) Answer the following questions: 1. Give an example which demonstrate each of the following: (a) Sound can travel through a gas……………………………………………………………………… (b) Sound can travel through a liquid. ……………………………………………………..………… (c) Sound can travel through a solid.…………………………………………………………………… (d) Objects that omit their own light ………………………………………………………………… 2. The diagrams below show the patterns produced on an oscilloscope by three different sound waves. (a) Which two waves have the same loudness?............................................................................................... (b) How do the diagrams show this? …………………………………………………………………………………………………………………..……………………
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…………………………………………………………………… (c) Which two waves have the same pitch?..................................………………………………………………….…………………… (d) How do the diagrams show this? …………………………………………………………………………………………………………………………………………
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……………………………………………………………… (e) Shuli is listening to a sound that produces the pattern below. Describe how the sound that Shuli hears changes between X and Y. …………………………………………………………………………………………………………………………………………
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……………………………………………………………….. 3. Jane played a musical instrument near a microphone connected to an oscilloscope. The diagrams below show the patterns made by four sounds. (i)
How does the sound shown in trace A differ from the sound in trace B? …………………………………………………………………………………………………………………………………………
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………………………………………………………………… (ii) How does the sound shown in trace A differ from the sound in trace C? …………………………………………………………………………………………………………………………………………
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………………………………………………………………… (iii) The pattern on the oscilloscope screen below represents the sound wave produced by an alarm. The loudness of the sound produced by the alarm decreases between X and Y. How can you tell this from the graph?………………………………………………………………………………………………………………………………
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………………………………………………………………… (ii) The pitch of the sound produced by the alarm stays the same between X and Y. How can you tell this from the graph? …………………………………………………………………………………………………………………………………………
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………………………………………………………………… 4. A sound wave travelling through air can be represented as shown in the diagram. (i)
Which distance, A, B, C, or D, represents: 
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One wavelength? …………………………………. The amplitude of the wave? ………………………………… (ii)
The cone of a loudspeaker is vibrating. The diagram shows how the air particles are spread out in front of the cone at a certain time. P is a compression, Q is a rarefaction. (a) Describe how the pressure in the air changes from P to Q. ..............................................................................................................................................
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......................................................................................................... (b) Describe the motion of the air particles as the sound wave passes. ..............................................................................................................................................
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Copy the diagram of air particles above and mark and label a distance equal to one wavelength of the sound wave.