NCERT Solutions For Class 8 Science Chapter 10 Sound LAQs
Question 1. The town hall building is situated close to Boojho’s house. There is a clock on the top of the town hall building that rings the bell every hour. Boojho has noticed that the sound of the clock appears to be much clearer at night. Explain
Answer:
We know that speed, pitch, and loudness are all initiated with a vibration. During the day, there are several vibrations around us. So, the sound coming from the clock gets disturbed, and the amplitude of vibrations becomes small.
But during the night, there are no such multiple vibrations in the environment. So, the sound is clearer. Further, the dew factor at night increases the speed of sound as the moisture level increases.
NCERT Class 8 Science Chapter 10 Sound LAQs
Question 2. An alarm bell is kept inside a vessel as shown in the figure. A person standing close to it can distinctly hear the sound of the alarm. Now, if the alt inside the vessel is removed completely, how will the loudness of the alarm be affected for the same person?
Answer:
Initially, the person can hear the sound coming from the air and water distinctly. But after some time, when the air is completely removed from the bottle, the sound will not pass through the vacuum in the glass. So, the man will not hear the sound that was coming through the air initially.
Question 3. How is sound produced, and how is it transmitted and heard by us?
Answer:
Sound is produced when any object starts vibrating by any means.
These vibrations travel from the sources all around the environment through the particles, and thus they reach their destination, i.e., our ear.
Now, it enters our ear and travels down a canal at the end of which a thin membrane is stretched tightly, known as the eardrum. The eardrum sends vibrations to the inner part of the ear, and finally reaches the brain, and we hear the sounds.
NCERT Solutions for LAQs on Sound Chapter 10
Question 4. Mention the property of vibrations that determines the pitch of the sound. Briefly explain along with some examples.
Answer:
The property that determines the shrillness or pitch of a sound is the frequency. If the frequency of vibration is higher, then we can say that the sound has a higher pitch. If the frequency of vibration is lower, we can say that the sound has a lower pitch.
Example: The drum vibrates with a low frequency.
Thus, it produces a low-pitched sound. Besides this, a whistle has a high frequency that produces a sound of a higher pitch. A bird makes a high-pitched sound while a lion makes a low-pitched roar. However, the roar of a lion is very loud while the sound of a bird is quite feeble.
NCERT Solutions for Sound Chapter 10
Question 5. Kanika switched ON the television to listen to her favourite music. After some time, she heard a loudspeaker sound coming from her neighbour’s house. Then, she switched OFF the television and closed her ears, so that the loudspeaker sound would not enter her ears.
- Slate the type of sound coming from the television.
- Explain how Kanika can distinguish between the categories of sound
- Mention whether the sound coming from the TV and the loudspeaker was audible or inaudible.
- Give the value displayed by Kanika here.
Answer: The sound of the music was coming from the television.
She realised after hearing both the sounds that the sound coming from the TV is pleasant and that ling from the loudspeaker outside is noisy and painful.
The sound coming from the TV and loudspeakers was in audible range, i.e., 20 Hz to 20 kHz.
The value displayed by Kanika is an attraction towards music and a hatred towards the loudspeakers.