 # Physics: Senior High School: 11th and 12th Grade Quiz - Waves - Sound (Questions)

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Sound energy travels as a longitudinal wave. Sound waves travel through a medium in a different way to electromagnetic waves, they require particles to travel across a distance. The particles vibrate in a series of compressions and rarefactions as the wave passes.

A compression is where the particles of the medium are pushed closer together by the wave and rarefactions are the opposite. The vibrations occur in the same direction as the wave is traveling. As the wave travels through the medium, the particles are displaced, but after the wave has passed, they are in the same position as they started. It is the energy carried by the wave that moves, not the particles. Sound is therefore a mechanical wave and cannot travel through a vacuum. This is why we can see the Sun but we can't hear it and is also partly why double and triple glazing in homes and offices reduces the sound coming from outside.

Sound waves have a frequency, wavelength, amplitude and period just like all waves. The frequency is the number of compressions (or rarefactions) that pass a given point in one second, the SI units are hertz (Hz). The wavelength is the distance from one point of a compression (or rarefaction) to the equivalent point on the next. The SI units are meters (m). The amplitude is really a measure of how much energy the wave is carrying, in other words its loudness. The period is the reciprocal of the frequency. Louder sounds carry more energy than quiet ones. There is another important term that you need to know about sound waves - pitch. This is how high or how low the note sounds and is determined by the frequency. A high-pitched note has a high frequency and vise versa. Sound whose pitch is so high that it cannot be heard by humans (above about 20 kHz) is called ultrasound and has several uses such as scanning developing babies in the womb and breaking up kidney stones. Sound that is too low-pitched to hear (below about 20 Hz) is called infrasound and is used for studying the heart and the structure of the Earth.

Sound waves can be reflected and diffracted quite easily. When sound is reflected, we call it an echo. One of the favorite echo questions in senior high school is to get you to calculate the distance from an object using data about an echo. What you must remember is that to hear an echo, the sound has traveled there and back. The biggest mistake that students make is not to divide the distance by two - but do pay attention to the wording of the question as sometimes you may be asked to calculate the distance the sound has traveled, there and back. The speed of sound in air is normally about 330 m/s but is much faster in denser media like water and solids.

Diffraction is one reason why you can hear sound from round a corner. When any wave touches an object that is about the same size at its wavelength, or passes through a gap that is about as wide as its wavelength, it diffracts - spreads out in a circular pattern from the edge of the object.

1. What kind of a wave is a sound wave?
 [ ] Latitudinal [ ] Electromagnetic [ ] Longitudinal [ ] Transverse
2. How do sound waves travel?
 [ ] Vibrations through a medium [ ] Via a carrier particle called a photon [ ] Via a carrier particle called a neutrino [ ] Sound waves can only travel in a vacuum
3. What is the pitch of a sound determined by?
 [ ] Its amplitude [ ] Its frequency [ ] The medium through which it travels [ ] Sound waves all have the same pitch
4. What is the loudness of a sound wave determined by?
 [ ] The medium through which it travels [ ] Its amplitude [ ] Its frequency [ ] Sound waves all have the same loudness
5. What are echoes?
 [ ] An impressionist repeating the noise [ ] Reflections of sounds [ ] Reflections of light [ ] Refraction of sounds
6. If a sound wave is made louder, what happens to the amount of energy the wave has?
 [ ] The energy increases [ ] The energy decreases [ ] The energy remains constant [ ] More information is required to answer the question
7. If the pitch of a sound wave is increased, does the time period between waveforms increase or decrease?
 [ ] Increases [ ] Decreases [ ] Remains the same [ ] Randomly changes to a discrete value
8. A car horn produces a sound wave of frequency 680 Hz. When the sound wave is traveling through air, it has a wavelength of 0.5 m. What is the speed of the sound wave?
 [ ] 300 m/s [ ] 330 m/s [ ] 340 m/s [ ] 400 m/s
9. The car horn and car unfortunately find themselves under water in a river. The car horn still produces a sound wave with a frequency of 680 Hz, however the speed of the sound is dramatically increased to 1485 m/s. What is the wavelength of the sound wave in water?
 [ ] 0.46 m [ ] 0.92 m [ ] 2.18 m [ ] 1,009,800 m
10. What is an ultrasound wave?
 [ ] An ultrasound wave is a sound wave which has a frequency higher than 20 kHz [ ] An ultrasound wave is a sound wave which has the same frequency as an audible sound wave, however it has much greater energy [ ] Ultrasound waves are transverse waves [ ] There are no such things as ultrasound waves Physics: Senior High School: 11th and 12th Grade Quiz - Waves - Sound (Answers)
1. What kind of a wave is a sound wave?
 [ ] Latitudinal [ ] Electromagnetic [x] Longitudinal [ ] Transverse
The energy and vibrations are in the same direction
2. How do sound waves travel?
 [x] Vibrations through a medium [ ] Via a carrier particle called a photon [ ] Via a carrier particle called a neutrino [ ] Sound waves can only travel in a vacuum
They are waves of alternating higher and lower pressure
3. What is the pitch of a sound determined by?
 [ ] Its amplitude [x] Its frequency [ ] The medium through which it travels [ ] Sound waves all have the same pitch
On the tonic sol-fa (doh, ray, mi etc) the first doh has a lower pitch than ray, which has a lower pitch than mi and so on
4. What is the loudness of a sound wave determined by?
 [ ] The medium through which it travels [x] Its amplitude [ ] Its frequency [ ] Sound waves all have the same loudness
A larger amplitude means the energy carried by the waves is bigger, but the frequency and wavelength remain the same
5. What are echoes?
 [ ] An impressionist repeating the noise [x] Reflections of sounds [ ] Reflections of light [ ] Refraction of sounds
Common examples used in senior high school are sonar from ships and submarines to measure depth, bats using echo location to find their prey and echoes in the mountains
6. If a sound wave is made louder, what happens to the amount of energy the wave has?
 [x] The energy increases [ ] The energy decreases [ ] The energy remains constant [ ] More information is required to answer the question
The pressure difference between compressions and rarefactions is greater
7. If the pitch of a sound wave is increased, does the time period between waveforms increase or decrease?
 [ ] Increases [x] Decreases [ ] Remains the same [ ] Randomly changes to a discrete value
Increasing the pitch means the sound wave vibrates more rapidly therefore there will be less time between the arrival of each successive compression or rarefaction
8. A car horn produces a sound wave of frequency 680 Hz. When the sound wave is traveling through air, it has a wavelength of 0.5 m. What is the speed of the sound wave?
 [ ] 300 m/s [ ] 330 m/s [x] 340 m/s [ ] 400 m/s
Light travels much faster so during a thunderstorm you see the lightning before hearing the thunder. If you count the time taken for the thunder to arrive after the flash, for every 3 seconds you count, the lightning was about one kilometer away
9. The car horn and car unfortunately find themselves under water in a river. The car horn still produces a sound wave with a frequency of 680 Hz, however the speed of the sound is dramatically increased to 1485 m/s. What is the wavelength of the sound wave in water?
 [ ] 0.46 m [ ] 0.92 m [x] 2.18 m [ ] 1,009,800 m
The denser the medium, the faster a sound wave will travel
10. What is an ultrasound wave?
 [x] An ultrasound wave is a sound wave which has a frequency higher than 20 kHz [ ] An ultrasound wave is a sound wave which has the same frequency as an audible sound wave, however it has much greater energy [ ] Ultrasound waves are transverse waves [ ] There are no such things as ultrasound waves
20 kHz is the average upper limit for human hearing. Many animals including cats, dogs and bats can hear ultrasound