CBSE Class 8 Science Chapter 10 Sound Short Answer Questions
Question 1. Suppose a stick is struck against a frying pan in a vacuum. Will the frying pan vibrate? Will we be able to hear the sound? Explain.
Answer: Yes, the flying pan will vibrate. Since, It Is being hit by the stick hut vibrations need .1 medium to travel, and there is no medium in a vacuum, so we cannot hear the vibrations produced.
Question 2. A stretched string, when set into vibration, produces the audible sound. Explain how?
Answer: A stretched string, on being set into vibration, forces the surrounding air to vibrate. This vibrating air in them affects our eardrum and produces an audible sound.
Read And Learn More CBSE Class 8 Science Short Answer Questions
Question 3. Astronauts in outer space have to use radios to communicate with one another. Why?
Answer: In outer space, there is no medium to help transmit sound. To communicate with one another, astronauts make use of electromagnetic waves such as radio waves, which can travel througha vacuum.
” Cbse Class 8 Science Chapter 10 Saqs “
Question 4. Two astronauts are floating close to each other in space. Can they talk to each other without using any special device? Give reasons.
Answer: No, they cannot talk to each other without using any special device because there is no medium in space, and sound needs a medium to travel.
Question 5. The sound produced by a mosquito is quite different from the roar of a lion. Explain the distinguishing points along with the reason.
Answer: A mosquito produces sound by the vibration of its wings in open air, while the lion roars by the vibration of its vocal cords.
” Sound Short Answer Questions Class 8 “
Due to this, the amplitude of the sound produced by a mosquito will be less than the sound produced by a lion, and even the pitch and quality of the two sounds are different, which makes the two sounds different and distinguishable.
Question 6. Explain the process, which bats use ultrasonic waves to catch prey.
Answer: The ultrasonic waves produced by the bats are high-pitched pitched are not heard by human beings. So, these ultrasonic waves, after striking the insect, send back an echo which is heard by the bat, and finally it gets over to the insect and catches it.
Question 7. Last Monday, Anita and her parents were going to the market by an auto rickshaw. On her way while taking a left turn, they heard the horn of a speeding truck towards the turn. Suddenly, the auto rickshaw driver stopped his vehicle by applying the brakes. Thus, by adopting the precautionary measure of blowing the horn, the truck driver saved lives.
- The loudness of a horn depends on what factor?
- Mention the values displayed by both the drivers
Answer: The factor on which the loudness of a horn sound depends is the amplitude of vibration of the horn.
The values displayed by both drivers are awareness and sensitivity.
” Vibrating Objects Produce Sound “
Question 8. We have learnt that vibration is necessary for producing sound. Explain why the sound produced by every vibrating body cannot be heard by us.
Answer: that the range of vibrations is different for different objects. But we can only hear the vibrations which lie between 20 Hz to 20000 Hz, so the sound of every vibration cannot be heard by us.
Question 9. We have a stringed musical instrument. The string is plucked in the middle first with a force of greater magnitude and then with a force of smaller magnitude. In which case would the instrument produce a louder sound?
Answer: It will create more louder sound in case the string is stretched with a greater force because the amplitude is greater in this case, and loudness depends on the amplitude. The greater the loudness, the greater will be the amplitude.
” Human Larynx And Vocal Cords “
Question 10. A simple pendulum makes 10 oscillations in 20 s. What is the period and frequency of its oscillations?
Answer: Given, number of oscillations =10
Time taken = 20 s
As we know, the number of oscillations per second is the frequency
⇒ \(\begin{aligned}
\text { Frequency } & =\frac{\text { Number of oscillations }}{\text { Time taken }} \\
& =\frac{10}{20}=0.5 \mathrm{~Hz}
\end{aligned}\)
⇒ \(\text { Time period }=\frac{1}{\text { Frequency }}=\frac{1}{0.5}=2 \mathrm{~s}\)
” Lightning And Thunder Explanation “
Question 11. 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. Can you explain why?
Answer: Lightning is seen earlier than the sound of thunder because light travels faster than sound. Hence, it reaches us before the sound does.