Sound Class 8 Worksheet Science Chapter 11

Q1: What brings the sound of a ringing telephone bell to our ears? 

Ans: The sound of a ringing telephone bell travels to our ears through the air in the room.

Q2: What is the audible range of frequencies for human ears? 

Ans: The audible range of frequencies for human ears is approximately:

• 20 Hz (lower limit)
• 20,000 Hz (upper limit)

Q3:  How does an object produce sound? 

Ans: Sound is produced when an object vibrates.

Vibration Produce SoundQ4:  Whose voice is shriller: a baby or a woman? 

Ans: The voice of a baby has a higher frequency (or higher pitch) than that of a woman due to which the voice of a baby is even more shrill than that of a woman.

Q5:  How is the sound produced in mridangam? 

Ans: When we strike the membrane of a mridangam, the sound produced is a result of:

• The vibration of the membrane.
• The vibration of the entire instrument.

This means that the sound we hear is not just from the membrane itself, but from the whole body of the mridangam vibrating together.

MridangamQ6:  What is the amplitude of oscillation? 

Ans: The maximum displacement of a vibrating object from its central position is called the amplitude of oscillation.

Q7:  How is pitch related to frequency? 

Ans: The frequency of a sound directly affects its pitch. Here’s how they relate:

• A higher frequency results in a shriller sound with a higher pitch.
• A lower frequency produces a sound with a deeper pitch.

For example:

• A drum has a low frequency, creating a low-pitched sound.
• A whistle has a high frequency, resulting in a high-pitched sound.

Q8: State one observation from everyday life which shows that sound travels slower than light.

Ans: Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. This shows that sound travels slower than light.

Lightning and ThunderQ9:  How can we distinguish between a man's voice and a woman's voice even without seeing them? 

Ans: We can distinguish between a man's voice and a woman's voice even without seeing them. This is because the voice of a woman has a higher frequency and is shriller than that of a man.

Q10:  Name the sound producing organ and organs of hearing in humans.

Ans: The sound-producing organ in humans is the larynx (voice box).

The organs of hearing in humans are the ears, which include three parts:

1. Outer ear 
2. Middle ear
3. Inner ear 

Q11:  How does loudness depend on the amplitude of vibrations? Explain.

Ans: 

 The loudness of sound is related to the amplitude of the vibrations that create it. Here are the key points:

• The loudness is proportional to the square of the amplitude.
• If the amplitude doubles, the loudness increases by a factor of four.
• Loudness is measured in decibels (dB).

In short,larger amplitudes result in louder sounds, while smaller amplitudes produce softer sounds.

Q12:  Out of the given instruments which produces the sound of a higher pitch: a drum or a whistle? Why? 

Ans: A drum produces a low-pitched sound because it vibrates at a low frequency. In contrast, a whistle emits a high-pitched sound due to its high frequency.

• Drum: Low frequency → Low pitch
• Whistle: High frequency → High pitch

Q13: How can you show that sound cannot travel through a vacuum?

Ans: To demonstrate that sound cannot travel through a vacuum, follow these steps:

• Take a metal or glass tumbler.
• Place a cell phone inside the tumbler.
• Ask a friend to call the cell phone from another phone and listen carefully.
• Cover the rim of the tumbler with your hands and place your mouth over the opening.
• Have your friend ring the phone again while you suck air out of the tumbler.
• Notice that the sound becomes fainter as you remove air.
• If you could remove all the air, the sound would stop completely.

This experiment shows that sound needs a medium to travel. When air is removed from the tumbler, it creates a vacuum, and sound cannot travel through it.

Q14:  How do we hear? 

Ans: The shape of the outer part of the ear is like a funnel. When sound enters in it, it travels down a canal at the end of which a thin membrane is stretched tightly. It is called the eardrum. The eardrum is like a stretched rubber sheet. Sound vibrations make the eardrum vibrate. The eardrum sends vibrations to the inner ear. From there, the signal goes to the brain. That is how we hear.