Study of Sound
Short Questions
1. What is sound?
- Sound is a form of energy that creates the sensation of hearing in our ears.
2. What type of wave is a sound wave?
- Sound wave is a longitudinal wave.
3. What is the direction of particle oscillation in a sound wave?
- Particles oscillate parallel to the direction of wave propagation.
4. What is the wavelength of a sound wave represented by?
- It is represented by the Greek letter lambda (λ).
5. What does the frequency of a sound wave determine?
- Frequency determines the pitch of the sound.
6. What does the amplitude of a sound wave determine?
- Amplitude determines the loudness of the sound.
7. What is the formula for the velocity of sound?
- Velocity of sound = wavelength × frequency (v = υλ).
8. In which medium does sound travel the fastest?
- Sound travels fastest in solids.
9. What is the velocity of sound in air at 25°C?
- The velocity of sound in air at 25°C is approximately 346 m/s.
10. How does the velocity of sound change with temperature?
- It increases with an increase in temperature.
11. What is the audible range of sound for humans?
- The audible range for humans is 20 Hz to 20,000 Hz.
12. What are sounds below 20 Hz called?
- Sounds below 20 Hz are called infrasound.
13. What are sounds above 20,000 Hz called?
- Sounds above 20,000 Hz are called ultrasound.
14. What is an echo?
- An echo is the repetition of sound due to reflection from a surface.
15. What is the minimum distance needed to hear a distinct echo at 22°C?
- The minimum distance is 17.2 m.
16. What is reverberation?
- Reverberation is the continuous reflection of sound in a closed space.
17. What does SONAR stand for?
- SONAR stands for Sound Navigation and Ranging.
18. What is sonography used for?
- Sonography is used to generate images of internal organs using ultrasound.
19. What part of the human ear collects sound waves?
- The outer ear, or pinna, collects sound waves.
20. What converts vibrations into electrical signals in the ear?
- The cochlea in the inner ear converts vibrations into electrical signals.
Long Questions
1. How does the velocity of sound depend on the temperature of the medium?
- The velocity of sound increases when the temperature of the medium rises because the particles move faster. For example, if the temperature increases by 1°C, the speed of sound in air increases by about 0.6 m/s.
2. Why does sound travel faster in solids than in gases?
- Sound travels faster in solids because the particles in solids are closely packed and can pass vibrations quickly. In gases, particles are far apart, so it takes more time for the vibrations to travel.
3. What is the difference between infrasound and ultrasound?
- Infrasound refers to sound waves with a frequency below 20 Hz, which humans cannot hear, like earthquake vibrations. Ultrasound has a frequency above 20,000 Hz and is used in technologies like sonography.
4. How does an echo work, and why can’t we hear it in a small room?
- An echo happens when sound reflects off a surface and comes back to us, but it needs a minimum distance of 17.2 m to be heard distinctly. In a small room, the distance is too short, so the sound mixes and we don’t hear a clear echo.
5. What is reverberation, and why is it a problem in some auditoriums?
- Reverberation is when sound waves reflect multiple times in a closed space, creating a continuous sound. In auditoriums, it can mix up sounds, making it hard to hear clearly, especially if the walls are not sound-absorbing.
6. How does SONAR help ships find objects underwater?
- SONAR uses ultrasonic waves that are sent into the water and reflect back after hitting an object, like a submarine. By measuring the time it takes for the waves to return, ships can calculate the distance to the object.
7. Why are ultrasound waves used in sonography for medical purposes?
- Ultrasound waves are used in sonography because they can penetrate the body and reflect off internal organs to create images. This helps doctors check things like a baby’s growth or heart conditions without causing harm.
8. How does the human ear help us hear sounds?
- The outer ear collects sound waves, the middle ear’s eardrum vibrates, and the inner ear’s cochlea turns these vibrations into electrical signals. These signals go to the brain through the auditory nerve, letting us hear.
9. Why are curved roofs used in movie theatres and conference halls?
- Curved roofs in movie theatres and conference halls help spread sound evenly by reflecting it in different directions. This reduces echoes and ensures everyone in the room can hear the sound clearly.
10. What happens to the velocity of sound in a gas if its density increases?
- If the density of a gas increases, the velocity of sound decreases because the speed is inversely proportional to the square root of density. For example, if the density becomes four times higher, the velocity reduces to half.
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