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: For the human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz.

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 that we hear is not only that of the membrane but of the whole body of the instrument.

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:  Who produces the sound of a higher pitch: a man or a woman? Why? 

Ans: Usually, the voice of a woman has a higher frequency and therefore, produces a sound of higher pitch.

Q8:  How is pitch related to frequency? 

Ans: The frequency determines the shrillness or pitch of a sound. If the frequency of vibration is higher we say that the sound is shrill and has a higher pitch. If the frequency of vibration is lower, we say that the sound has a lower pitch.

Q9: 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 ThunderQ10:  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.

Q11:  Why are the voices of men, women, and children different? 

Ans: The vocal cords in men are about 20mm long. In women, these are about 5mm shorter. Children have very short vocal cords. This is the reason why the voices of men, women, and children are different.

Q12:  How does loudness depend on the amplitude of vibrations? 

Ans: The loudness of sound is proportional to the square of the amplitude of the vibration producing the sound. For example, if the amplitude becomes twice, the loudness increases by a factor of 4.

Q13:  Which produces the sound of a higher pitch: a drum or a whistle? Why? 

Ans: A drum vibrates with a low frequency. Therefore, it produces a low-pitched sound. On the other hand, a whistle has a high frequency and therefore, produces a sound of higher pitch.

Q14: How can you show that sound cannot travel through a vacuum?

Ans: Take a metal glass tumbler. Place a cell phone in it. Ask your friend to give a ring on this cell phone from another cell phone. Listen to the ring carefully. Now, surround the rim of the tumbler with your hands. Put your mouth on the opening between your hands. Indicate to your friend to give a ring again. Listen to the ring while sucking air from the tumbler. You will observe that the sound become fainter as you suck. If you had been able to suck all the air in the tumbler, the sound would stop completely. Actually, sound needs a medium to travel. When air has been removed completely from a vessel, it is said that there is vacuum in the vessel. The sound cannot travel through vacuum.

Q15:  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.