Sound

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Sound Waves

Sound waves are produced by vibrating sources.
A medium is required to transmit sound; sound cannot travel through a vacuum.
Sound waves are longitudinal waves consisting of compressions (high pressure) and rarefactions (low pressure).
When a sound wave meets a solid, the vibrations are transferred to the solid (e.g., can shatter glass).

Compressions and rarefactions

Measuring the Speed of Sound

Speed of sound in air ≈ 340 m/s; fastest in solids (~5000 m/s), slowest in gases.
Experiment 1: Two people at measured distance (e.g., 100 m); one bangs blocks, other starts stopwatch on sight and stops on sound. Repeat and average time.
Experiment 2: Two microphones connected to an oscilloscope placed ~2 m apart; clap near first mic; oscilloscope measures time difference between mic signals.
Speed = distance / time. Experiment 2 is more accurate because timing is automatic.
Random errors in Experiment 1 due to reaction time; use larger distances and repeat readings to reduce error.

Measuring the speed of sound between two points

Pitch and Loudness

Frequency determines pitch: high frequency → high pitch; low frequency → low pitch.
Amplitude determines loudness: large amplitude → loud sound; small amplitude → quiet sound.
Sound waves reflect off hard surfaces; the reflected sound is called an echo.

Pitch and amplitude of a sound wave

Ultrasound

Human hearing range: 20 Hz to 20 kHz (decreases with age).
Ultrasound is sound with frequency higher than 20 kHz.
Ultrasound is used in medical imaging (e.g., sonograms) and industrial testing.

Frequencies of ultrasound

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練習題

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1.What type of wave is a sound wave?
Easy
- ATransverse
- BLongitudinal
- CElectromagnetic
- DStationary
2.Sound waves can travel through a vacuum.
Easy
True or false?
3.Complete the sentence.
Easy
Sound waves consist of regions of higher pressure called ____ and regions of lower pressure called ____.
4.State the approximate range of frequencies audible to humans.
Easy
5.Which of the following materials does sound travel fastest through?
Easy
- AAir
- BWater
- CSteel
- DVacuum
6.A sound wave with a high frequency has a low pitch.
Easy
True or false?
7.Match each term to its correct description.
Medium
- Amplitude
- Frequency
- Wavelength
- Determines loudness
- Determines pitch
- Distance between compressions
8.Arrange the following media in order of increasing speed of sound (slowest first).
Easy
- Gas
- Liquid
- Solid

更多題目

9.What is ultrasound?
Easy
- ASound with frequency below 20 Hz
- BSound with frequency above 20 kHz
- CSound with very high amplitude
- DSound that travels faster than 340 m/s
10.Sound waves are produced by which of the following?
Easy
- AVibrating sources
- BStationary objects
- CElectromagnetic fields
- DThermal energy
11.In which medium does sound travel fastest?
Easy
- ASolid
- BLiquid
- CGas
- DVacuum
12.Which of the following is the approximate speed of sound in air?
Easy
- A340 m/s
- B1500 m/s
- C5000 m/s
- D300 000 000 m/s
13.A sound wave has a high frequency. What does this indicate about its pitch?
Easy
- AHigh pitch
- BLow pitch
- CLoud volume
- DSoft volume
14.A sound wave with a large amplitude has a high volume.
Easy
True or false?
15.What is an echo?
Easy
- AThe reflection of a sound wave off a hard surface
- BThe absorption of a sound wave by a soft surface
- CThe refraction of a sound wave as it enters a different medium
- DThe diffraction of a sound wave around an obstacle
16.Ultrasound is defined as sound with a frequency higher than:
Easy
- A20 kHz
- B20 Hz
- C2000 Hz
- D200 kHz
17.The human hearing range decreases with age.
Easy
True or false?
18.Which of the following are true about sound waves? (Select all that apply)
Medium
- AThey are longitudinal waves.
- BThey can travel through a vacuum.
- CThey consist of compressions and rarefactions.
- DThey are transverse waves.
19.Sound waves are transverse waves.
Easy
True or false?
20.A student claps 100 m away from a wall and hears the echo after 0.59 s. What is the speed of sound in air?
Medium
- A340 m/s
- B170 m/s
- C590 m/s
- D200 m/s
21.Which of the following is not a property of a sound wave?
Easy
- AIt can travel through a vacuum.
- BIt is a longitudinal wave.
- CIt can be reflected.
- DIt requires a medium to travel.
22.Which of the following increase the accuracy of measuring the speed of sound in air? (Select all that apply)
Medium
- AUsing a larger distance between the sound source and receiver.
- BUsing a stopwatch with a resolution of 0.01 s.
- CUsing an oscilloscope to measure time automatically.
- DTaking multiple readings and averaging.
23.A student measures the speed of sound in air using an oscilloscope and two microphones placed 3.0 m apart. The oscilloscope shows the sound reaches the first microphone at 0.000 s and the second microphone at 0.0088 s. What is the speed of sound calculated from these measurements?
Medium
- A341 m/s
- B340 m/s
- C300 m/s
- D375 m/s
24.In an experiment to measure the speed of sound using two microphones and an oscilloscope, the time base is set to 5 ms per division. The trace shows the sound reaching the first microphone at 0 divisions and the second microphone at 1.8 divisions. The microphones are 3.0 m apart. What is the speed of sound?
Medium
- A333 m/s
- B340 m/s
- C300 m/s
- D360 m/s
25.A student claps 85 m from a wall and hears the echo 0.50 s later. What is the speed of sound in air?
Easy
- A340 m/s
- B170 m/s
- C680 m/s
- D85 m/s
26.A student uses a stopwatch to measure the time for an echo from a cliff 150 m away. The student claps and starts the stopwatch, and stops it when the echo is heard. The reading is 0.88 s. Which statement about this measurement is correct?
Medium
- AThe measured time is likely to be too short due to reaction time.
- BThe measured time is likely to be too long due to reaction time.
- CThe speed of sound calculated from this measurement will be 341 m/s.
- DThe experiment is more accurate than using an oscilloscope.
27.Which of the following are true about the speed of sound? (Select all that apply)
Medium
- ASound travels fastest in solids.
- BSound travels slowest in gases.
- CSound travels at about 340 m/s in air.
- DSound travels at about 1500 m/s in solids.
- ESound cannot travel through a vacuum.
28.In an experiment to measure the speed of sound using an oscilloscope and two microphones, which of the following is the main advantage over using a stopwatch and two people?
Easy
- AIt eliminates the need to measure distance.
- BIt automatically measures the time difference, reducing reaction time errors.
- CIt works in a vacuum.
- DIt gives a direct reading of speed in m/s.
29.A student uses a stopwatch to measure the time for sound to travel 100 m. The student starts the stopwatch when they see a clap and stops it when they hear the echo from a wall 50 m away. The measured time is 0.30 s. Why is this method less accurate than using an oscilloscope?
Medium
- AThe distance is too small.
- BHuman reaction time introduces a significant error because the time interval is short.
- CThe echo is too quiet to hear accurately.
- DThe stopwatch has a resolution of only 0.1 s.
30.In an experiment to measure the speed of sound using an oscilloscope and two microphones, which of the following would increase the accuracy of the measurement? (Select all that apply)
Medium
- AUsing a larger distance between the microphones.
- BUsing a smaller distance between the microphones.
- CTaking repeat readings and calculating an average time.
- DUsing a time base with a smaller scale (e.g., 0.5 ms/div instead of 2 ms/div).
- EUsing a single microphone and measuring the time for the sound to travel to a wall and back.
31.Sound travels faster in liquids than in gases but slower than in solids.
Easy
True or false?
32.Arrange the following steps in the correct order for measuring the speed of sound using an oscilloscope and two microphones.
Medium
- Make a loud clap near the first microphone.
- Measure the distance between the two microphones using a tape measure.
- Connect the two microphones to the oscilloscope.
- Read the time difference between the two signals on the oscilloscope.
- Calculate speed using speed = distance / time.
33.A sound wave has a frequency of 256 Hz and a wavelength of 1.33 m in air. What is the speed of sound in air?
Medium
- A192 m/s
- B340 m/s
- C341 m/s
- D342 m/s
34.Ultrasound is sound with a frequency lower than 20 Hz.
Easy
True or false?
35.Match each sound wave property to its correct description.
Easy
- Frequency
- Amplitude
- Wavelength
- Related to loudness
- Related to pitch
- Distance between successive compressions
36.Sound waves travel fastest in gases.
Easy
True or false?
37.What is the approximate range of frequencies audible to humans?
Easy
- A20 Hz to 20 000 Hz
- B200 Hz to 2000 Hz
- C20 kHz to 200 kHz
- D2 Hz to 200 Hz
38.A student uses an oscilloscope and two microphones to measure the speed of sound. The microphones are placed 2.0 m apart. The oscilloscope trace shows the sound reaching the first microphone at 0.0 ms and the second microphone at 5.8 ms. What is the speed of sound calculated from these readings?
Medium
- A290 m/s
- B340 m/s
- C345 m/s
- D350 m/s
39.In an experiment to measure the speed of sound using an oscilloscope and two microphones, the microphones are placed 3.0 m apart. The oscilloscope time base is set to 2 ms per division. The sound reaches the first microphone at the trigger point and reaches the second microphone 2.5 divisions later. What is the speed of sound?
Medium
- A600 m/s
- B340 m/s
- C1500 m/s
- D1200 m/s
40.A student measures the speed of sound using two microphones connected to an oscilloscope. Which of the following actions would increase the accuracy of the measurement? (Select all that apply)
Medium
- AUsing a larger distance between the microphones
- BUsing a smaller distance between the microphones
- CRepeating the experiment and calculating an average time
- DUsing a time base with a smaller scale (e.g., 1 ms/div instead of 5 ms/div)
41.Fill in the blanks to describe the nature of sound waves.
Easy
Sound waves are ____ waves. They travel as a series of ____ and ____.
42.Complete the sentence about the human hearing range.
Easy
The approximate range of frequencies audible to humans is ____ Hz to ____ Hz.
43.Complete the sentence about ultrasound.
Easy
Ultrasound is sound with a frequency higher than ____ kHz.
44.A sound wave travels 340 m in 1.0 s. What is its speed?
Easy
45.A sound wave has a frequency of 440 Hz and a wavelength of 0.78 m. Calculate the speed of the sound wave.
Medium
46.Complete the sentence about the speed of sound.
Easy
Sound travels fastest in ____ and slowest in ____.
47.Complete the sentence about the nature of sound waves.
Easy
Sound waves are ____ waves, consisting of regions of high pressure called ____ and regions of low pressure called ____.
48.State one reason why measuring the speed of sound using a stopwatch and two people is less accurate than using an oscilloscope and two microphones.
Medium
49.Describe how you would measure the speed of sound in air using an oscilloscope and two microphones. Include the equipment, method, and how you would calculate the speed.
Hard
50.Explain why sound cannot travel through a vacuum.
Easy
51.A sound wave travels 340 m in 1.0 s. What is its speed?
Easy
- A340 m/s
- B306 m/s
- C374 m/s
- D408 m/s
52.A sound wave has a frequency of 440 Hz and a wavelength of 0.78 m. Calculate the speed of the sound wave.
Medium
- A309 m/s
- B377 m/s
- C343 m/s
- D411 m/s

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