1. How does the sound produced by a vibrating object in a medium reach your ear?
Ans: When an object vibrates, it causes the particles of the surrounding medium (such as air, water, or solids) to vibrate as well. The vibrating particles then transfer this energy to adjacent particles, causing them to vibrate. This chain reaction of vibrations continues, and the sound waves travel through the medium. Eventually, the sound reaches your ear, where it is detected as sound. The process relies on the transmission of vibrations from one particle to the next until it reaches your auditory system.
2. Explain how sound is produced by your school bell.
Ans: When the school bell is struck with a hammer, it vibrates back and forth. These vibrations create alternating regions of compression and rarefaction in the surrounding air. Compression occurs when the particles of air are pushed together, while rarefaction occurs when the particles are spread apart. The rapid movement of the bell produces sound waves that travel through the air, and when these sound waves reach your ear, you hear the bell ringing. The vibrating bell thus converts mechanical energy into sound energy.
3. Why are sound waves called mechanical waves?
Ans: Sound waves are called mechanical waves because they require a medium (such as air, water, or solids) to propagate. These waves interact with the particles of the medium, causing them to vibrate and transfer energy. Since sound cannot travel through a vacuum (where there are no particles to vibrate), it is classified as a mechanical wave.
4. Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?
Ans: No, you will not be able to hear any sound produced by your friend on the moon. Sound waves require a medium (like air, water, or solids) to propagate. Since the moon has no atmosphere and sound cannot travel through the vacuum of space, there would be no medium for the sound to travel through. Therefore, even if your friend makes a sound, you would not be able to hear it.
5. Which wave property determines (a) loudness, (b) pitch?
Ans:
(a) Amplitude – The loudness of the sound is directly related to its amplitude. A sound with a larger amplitude is perceived as louder, while a smaller amplitude results in a quieter sound.
(b) Frequency – The pitch of the sound is directly related to its frequency. A high-frequency sound corresponds to a high pitch, while a low-frequency sound corresponds to a low pitch.
6. Guess which sound has a higher pitch: guitar or car horn?
Ans:
The pitch of a sound is directly proportional to its frequency. The guitar generally produces higher-frequency sounds compared to a car horn, which typically produces lower-frequency sounds. Therefore, the guitar has a higher pitch compared to the car horn.
7. What are the wavelength, frequency, time period, and amplitude of a sound wave?
Ans:
(a) Wavelength – Wavelength is the distance between two consecutive rarefactions or compressions in a sound wave. The SI unit of wavelength is meter (m).
(b) Frequency – Frequency is the number of oscillations or vibrations of a sound wave per second. The SI unit of frequency is hertz (Hz).
(c) Amplitude – Amplitude is the maximum displacement of the particles in the medium from their equilibrium position due to the sound wave. It represents the maximum height of the wave’s crest or depth of its trough.
(d) Time period – The time period is the time taken for one complete cycle of a sound wave. It is the inverse of frequency and is measured in seconds (s).
8. How are the wavelength and frequency of a sound wave related to its speed?
Ans:
Wavelength, speed, and frequency are related in the following way:
Speed = Wavelength x Frequency
v = λ ν