RBSE Solutions Class 8 Science Chapter 10 Sound

I. Multiple Choice Questions

 

Question 1. In which medium, the transmission of sound is not possible?
(a) Iron rod
(b) Water
(c) Air
(d) Vacuum
Answer: (d) Vacuum
In simple words: Sound needs something to travel through, like air, water, or a solid. It cannot travel in empty space because there are no particles to carry the vibrations.

🎯 Exam Tip: Remember that sound is a mechanical wave, meaning it requires a medium for propagation, unlike light waves.

 

Question 2. The up-down motion around the mean position of an object is called
(a) Vibration
(b) Amplitude
(c) Frequency
(d) Periodic time
Answer: (a) Vibration
In simple words: When an object moves back and forth quickly from its central, calm position, this movement is called vibration. It's how sound is often made.

🎯 Exam Tip: Understand that vibration is the fundamental cause of sound production.

 

Question 3. Speed of sound at 0°C in air is
(a) 350 m/sec
(b) 200 m/sec
(c) 400 m/sec
(d) 331 m/sec
Answer: (d) 331 m/sec
In simple words: At freezing point (0°C), sound travels through the air at a speed of 331 meters every second. This speed changes a little if the temperature of the air is different.

🎯 Exam Tip: The speed of sound varies with the medium and temperature, being generally faster in solids than liquids, and faster in liquids than gases.

 

Question 4. Time taken to complete one vibration is called-
(a) frequency
(b) time period
(c) amplitude
(d) none of these
Answer: (b) time period
In simple words: The "time period" is simply how long it takes for a vibrating object to go through one full back-and-forth cycle. It's measured in seconds.

🎯 Exam Tip: Time period and frequency are inversely related; a longer time period means a lower frequency.

 

Question 2. In the following statements, tick (T) against those which are true, and (F) against those which are false:
Answer:
1. True
2. False
3. True
4. True.
In simple words: For each statement, decide if it is correct or incorrect. If it is correct, mark it as 'True', and if it is incorrect, mark it as 'False'.

🎯 Exam Tip: Always read each statement carefully and consider if it aligns with scientific facts or definitions before marking it true or false.

 

Question 3. Fill in the blanks.
1. Main source of sound in human is ...............
2. The sound waves having frequency more than 20,000 hertz are called ...............
3. The international unit of frequency is ...............
4. The loudness of sound depends on ...............
5. The pitch of sound depends on ...............
Answer:
1. Larynx
2. Ultrasonic Sound
3. Hertz
4. Amplitude of vibration
5. Frequency
In simple words: The larynx is where human voice comes from. Sounds above 20,000 Hz are called ultrasonic. Hertz is the unit for how many times something vibrates per second. How loud a sound is depends on its amplitude, and how high or low its pitch is depends on its frequency.

🎯 Exam Tip: Knowing the key terms related to sound (larynx, ultrasonic, hertz, amplitude, frequency) is crucial for filling in these blanks correctly.

Sound Short Answer Type Questions

 

Question 1. A musical instrument takes 2 seconds to complete 200 oscillations then calculate frequency of it.
Answer:
To calculate the frequency, we use the formula:
Frequency \( = \frac{\text{Total number of vibrations}}{\text{Time taken in vibrations}} \)
Here, total number of vibrations = 200
Time taken = 2 seconds
So, Frequency \( = \frac{200}{2 \text{ sec}} \)
Frequency \( = 100 \) vibration/sec. or Hertz.
This means the instrument completes 100 back-and-forth movements every second.
In simple words: You can find how often something vibrates by dividing the total number of its movements by the time it took. In this case, it vibrates 100 times in one second.

🎯 Exam Tip: Always remember the formula for frequency, \( \text{Frequency} = \frac{\text{Number of oscillations}}{\text{Time}} \), and state the unit as Hertz (Hz) or vibrations/second.

 

Question 3. What are differences in audible, infra-audible, ultra-audible.
Answer:
The human ear can hear sounds within a specific frequency range.
* **Infrasonic vibrations:** These are vibrations with a frequency less than 20 Hz. Humans cannot hear these sounds. For example, elephants and whales use infrasound to communicate over long distances. * **Audible (or sonic) vibrations:** These are vibrations with a frequency between 20 Hz and 20,000 Hz. These are the sounds that humans can hear. Most everyday sounds fall into this category. * **Ultrasonic vibrations:** These are vibrations with a frequency above 20,000 Hz. Humans cannot hear these sounds either. Animals like bats and dolphins use ultrasound for navigation and hunting.
The higher the frequency of sound, the sharper or shriller it sounds to our ears within the audible range.
In simple words: Sounds we can hear are "audible". Sounds too low for us to hear are "infrasonic". Sounds too high for us to hear are "ultrasonic". Each type has a different vibration speed.

🎯 Exam Tip: Clearly define the frequency range for each type of sound and state whether humans can perceive them or not. Giving examples of animals that use these sounds can strengthen your answer.

 

Question 4. Define frequency and periodic time. Represent the relation of them by a formula.
Answer:
* **Frequency:** Frequency is the number of complete vibrations or oscillations that occur in one second. It tells us how often something vibrates. * **Time period:** Time period is the time needed to complete one full oscillation or vibration. It tells us how long one cycle takes.
The relationship between frequency (f) and time period (T) is:
\( \text{Time period} = \frac{1}{\text{Frequency}} \)
Or, inversely:
\( \text{Frequency} = \frac{1}{\text{Time period}} \)
This means if you know one, you can easily find the other, as they are inverses of each other.
In simple words: Frequency is how many times something shakes in one second. Time period is how many seconds one shake takes. They are opposite numbers of each other.

🎯 Exam Tip: Define both terms precisely and write down the formula clearly. Remember that frequency is measured in Hertz (Hz) and time period in seconds (s).

Sound Long Answer Type Questions

 

Question 1. Draw an human vocal system diagram and explain its working principle.
Answer:
*(Note: A diagram of the human vocal system would typically be drawn here, but is not provided in the source text. The following explanation describes its working principle.)*
Sound in humans is made by the voice box, also known as the larynx, which is located in the throat. Just below the larynx is the windpipe. Inside the larynx, there are two special folds of tissue called vocal cords. These cords are stretched across the voice box, leaving a small opening, or slit, between them. When air from the lungs is forced through this narrow slit, the vocal cords start to vibrate. These vibrations then create the sound that we hear.
In simple words: Our voice comes from the voice box in our throat. Air from our lungs makes two small cords inside it shake, and this shaking creates sound.

🎯 Exam Tip: When explaining the vocal system, highlight the key parts: larynx, vocal cords, and lungs, and describe how their interaction produces sound through vibration.

 

Question 2. What is noise pollution? How does it affect us? How can it controlled? Explain it in detail.
Answer:
Noise pollution happens when unwanted, loud, and harsh sounds fill the environment from various sources, causing disturbance. This type of pollution became very common in the 20th century due to our increasing use of different machines at home, in factories, and at work.
The amount of noise pollution in a place depends on:
(a) How loud the sound is.
(b) How long the noise lasts in that area.

**Harmful effects of noise pollution:**
1. Too much noise around us makes it hard to talk and hear other people speak clearly. 2. If someone is exposed to a lot of noise for a long time, it can lead to hearing loss or even deafness. 3. Noise can make it difficult to focus, which then lowers how well we work. 4. Noise can cause anger and stress, and it can disturb a person's sleep, making them tired. 5. It can lead to headaches, make people easily annoyed, and cause nervous tension. 6. Noise can also affect vision, possibly causing a loss of night vision or problems with seeing colors.

**Preventive and control measures for noise:**
While we cannot completely remove all noise in modern society, we can lower its harmful levels by taking these steps:
1. Machines should be designed to make as little noise as possible. 2. All vehicles and generators should have better silencers to reduce sound. 3. Heavy vehicles should not be allowed to drive in areas where people live. 4. Using loudspeakers for parties or religious events should be stopped. 5. Factories should be built far away from places where people live. 6. At home, TVs, radios, and music systems should always be played at a low volume.
In simple words: Noise pollution is loud, annoying sound that harms us. It makes it hard to hear, causes stress, and can even damage our hearing. We can control it by making machines quieter, using silencers, keeping loud vehicles out of residential areas, limiting loudspeakers, moving factories away from homes, and playing music softly.

🎯 Exam Tip: When answering about noise pollution, clearly define it, list its harmful effects, and provide practical solutions for its prevention and control.

 

Question 3. Exceiving the sound signals to brain with labelled diagram of human ear.
Answer:
The human ear is a complex organ designed to receive sound vibrations and send them to the brain. Below is a simplified diagram illustrating its main parts.

The outer ear (pinna) catches sound vibrations and guides them into the ear canal. These vibrations then hit a stretched membrane called the eardrum, causing it to vibrate. From the eardrum, the vibrations move to the middle ear. The middle ear has three tiny, delicate bones: the hammer, anvil, and stirrup. These bones work together to pass the vibrations along to the inner ear. The inner ear contains a coiled tube known as the cochlea. Inside the cochlea are tiny hairs suspended in a fluid. These hairs detect the vibrations from the middle ear and convert them into electrical signals. These electrical signals are then sent to the brain through the auditory nerve, allowing us to interpret them as sound.
In simple words: The outer ear collects sounds, which make the eardrum shake. These shakes move through small bones in the middle ear to a spiral tube in the inner ear. Tiny hairs in this tube turn the shakes into messages that go to our brain, and that's how we hear.

🎯 Exam Tip: Focus on the sequence of sound transmission through the outer, middle, and inner ear, identifying the key structures and their roles in converting sound waves into electrical signals for the brain.

 

Question 4. How is sound transmitted in solid and gases? Explain it.
Answer:
Sound needs a medium (like a solid, liquid, or gas) to travel. It cannot travel in a vacuum.
(a) **Sound transmission in gas (e.g., air):** Sound travels through air starting from its source and reaching our ears. When an object vibrates, it causes the air particles around it to vibrate as well. Each vibrating air particle then bumps into the next one, passing on the vibration. This creates a wave of sound that moves through the air. When this sound wave reaches our ear, it makes the eardrum vibrate, and we hear the sound. (b) **Sound transmission in solid:** Sound can also travel through solids. For example, if you place one end of a metal scale on your ear and have a friend lightly rub the other end with nails, you will hear the sound. This happens because the vibrations created at one end of the scale travel through the solid material to the other end. This shows that sound can travel through solid objects efficiently. In labs, when a tuning fork vibrates, sound is heard if it is brought close to the ear, even without directly touching it to a solid.
In simple words: In gases like air, sound moves as air particles bump into each other. In solids, sound travels through the shaking of the solid material itself, like a metal rod. Sound waves need particles to pass their energy along.

🎯 Exam Tip: When explaining sound transmission, emphasize that it's the vibration of particles in the medium that carries the sound energy, and provide clear, simple examples for both gases and solids.

Sound Additional Questions Solved

I. Multiple Choice Questions

 

Question 2. Speed of sound is least in:
(a) Solid
(b) Liquid
(c) Gas (air)
(d) None of these
Answer: (c) Gas (air)
In simple words: Sound travels slowest in gases like air because the particles are far apart. It travels fastest in solids and a bit slower in liquids.

🎯 Exam Tip: Remember the general rule: sound travels fastest in solids, then liquids, and slowest in gases, due to the density and arrangement of particles in each medium.

 

Question 3. The number of virbration/oscillation executed per second is known as:
(a) Frequency
(b) Amplitude
(c) Wave length
(d) Pitch
Answer: (a) Frequency
In simple words: The number of times something vibrates or moves back and forth in one second is called its frequency. This is what determines the pitch of a sound.

🎯 Exam Tip: Understand that frequency is a measure of how often an event occurs per unit of time, and its SI unit is Hertz (Hz).

 

Question 4. The S.I unit of frequency is in
(a) m/s
(b) Hertz
(c) Per second
(d) None of these
Answer: (b) Hertz
In simple words: The standard way to measure frequency is in units called Hertz, which means "cycles per second."

🎯 Exam Tip: Always use the correct SI units for physical quantities; for frequency, it is Hertz (Hz).

 

Question 5. Loudness of sound depends upon-
(a) Wave length
(b) Speed of sound
(c) Amplitude
(d) None of these
Answer: (c) Amplitude
In simple words: How loud a sound is depends on its amplitude. A bigger amplitude means a louder sound, and a smaller amplitude means a softer sound.

🎯 Exam Tip: Distinguish between loudness (related to amplitude) and pitch (related to frequency) of sound waves.

 

Question 6. The sound of frequency less than 20 Hertz is known as
(a) Ultra sonic
(b) **[Missing Option Text]**
Answer: (b) [missing option text]
In simple words: Sounds that vibrate less than 20 times per second are too low-pitched for humans to hear. These are called infrasonic sounds.

🎯 Exam Tip: Recall the human audible range (20 Hz to 20,000 Hz) and categorize sounds outside this range as infrasonic (below 20 Hz) or ultrasonic (above 20,000 Hz).

 

Question 8. The sound in the audible range is called-
(a) Ultra sonic
(b) Sonic
(c) Sub sonic
(d) Light sound
Answer: (b) Sonic
In simple words: Sounds that humans can hear, between 20 Hz and 20,000 Hz, are known as sonic sounds.

🎯 Exam Tip: "Sonic" is the term specifically used for sounds within the human hearing range.

 

Question 9. Eardrum is a part of
(a) Hearing organ
(b) Sound producing organ
(c) Muscular system
(d) None of these
Answer: (a) Hearing organ
In simple words: The eardrum is a very important part of our ear, which is the organ we use for hearing. It vibrates when sound waves hit it.

🎯 Exam Tip: Identify the eardrum as a key component of the hearing process, specifically located in the middle ear.

 

Question 10. The pitch of sound depends upon the
(a) amplitude
(b) wave velocity
(c) wave length
(d) frequency
Answer: (d) frequency
In simple words: The pitch of a sound, whether it sounds high or low, is directly decided by how fast the sound waves vibrate, which is called frequency.

🎯 Exam Tip: Remember that high-frequency sounds have a high pitch, and low-frequency sounds have a low pitch.

 

Question 11. The outer part of human ear is called
(a) Pinna
(b) Ear drum
(c) Tympanum
(d) None of these
Answer: (a) Pinna
In simple words: The part of your ear that you can see outside your head is called the pinna. It helps collect sound waves.

🎯 Exam Tip: Know the different parts of the ear and their specific names, especially the external visible part, the pinna.

 

Question 13. Relation between frequency and time period is-
(a) Time period = frequency
(b) (Frequency)2 = time period
(c) Frequency = \( \frac{1}{\text{Time period}} \)
(d) Frequency = \( \frac{\text{Time period}}{2} \)
Answer: (c) Frequency = \( \frac{1}{\text{Time period}} \)
In simple words: Frequency and time period are opposite values. If you know one, you can find the other by taking "one divided by" that number.

🎯 Exam Tip: This inverse relationship is fundamental in wave mechanics; ensure you can write both forms of the equation \( f = 1/T \) and \( T = 1/f \).

 

Question 14. The voice box is also known as
(a) Mouth
(b) Larynx
(c) Heart
(d) Stomach
Answer: (b) Larynx
In simple words: The larynx is the scientific name for the voice box, which is where humans make sounds for speaking and singing.

🎯 Exam Tip: Associate the larynx with the production of sound in humans, as it contains the vocal cords.

 

Question 15. A pendulum oscillates 20 times in 2 seconds then its time period is
(a) 0.01 sec
(b) 0.001 sec
(c) 0.02 sec
(d) 0.1 sec
Answer: (d) 0.1 sec
In simple words: To find the time for one swing, divide the total time by the number of swings. If it swings 20 times in 2 seconds, then each swing takes 0.1 seconds.

🎯 Exam Tip: The time period \( T \) is calculated as \( \text{Time taken} / \text{Number of oscillations} \). In this case, \( T = 2 / 20 = 0.1 \) s.

Sound Very Short Answer Type Questions

 

Question 1. What is sound?
Answer: Sound is a form of energy that usually creates the feeling of hearing in our ears. It travels as waves through a medium.
In simple words: Sound is a type of energy that lets us hear things.

🎯 Exam Tip: Define sound as a form of energy and mention its ability to cause the sensation of hearing.

 

Question 2. What is the most common medium through which sound travels?
Answer: Air is the most common medium through which sound travels to us. Although sound can travel through other mediums like water and solids, air is what we encounter most frequently.
In simple words: Air is the most common thing sound travels through.

🎯 Exam Tip: Recognize that while sound can travel through various mediums, air is the primary one we interact with daily.

 

Question 3. Can sound propagate through vacuum?
Answer: No, sound cannot travel through a vacuum. It needs a material medium, such as air, water, or a solid, for its propagation because it travels by vibrating particles.
In simple words: No, sound cannot travel in empty space because there is nothing for it to vibrate through.

🎯 Exam Tip: Emphasize that sound is a mechanical wave and therefore requires a material medium to propagate, unlike electromagnetic waves like light.

 

Question 4. What is time period? Write its S.I unit.
Answer: The time period (T) is the time it takes for one complete oscillation or vibration to happen in a medium. It is denoted by the capital letter T. Its S.I unit is the second (s). The duration of one full cycle of any periodic event is its time period.
In simple words: Time period is how long one full shake or swing takes. It is measured in seconds.

🎯 Exam Tip: Clearly define time period as the duration of one complete cycle and remember its SI unit, the second.

 

Question 5. What is frequency? How is it represented? Write its S.I unit.
Answer: Frequency is the number of vibrations or oscillations that occur per second in a wave. It is often represented by the symbol \( \nu \) (nu) or \( f \). Its S.I unit is Hertz (Hz). One Hertz means one vibration per second. This value helps understand how high or low a sound's pitch is.
In simple words: Frequency is how many times a wave vibrates in one second. It's shown by \( \nu \) or \( f \) and measured in Hertz.

🎯 Exam Tip: Define frequency as the rate of oscillation, state its symbol ( \( \nu \) or \( f \) ), and its SI unit (Hertz).

 

Question 6. W Processing math: 100% he term loudness?
Answer: The maximum displacement of a vibrating object from its central, calm position is called amplitude. Loudness is related to this amplitude.
In simple words: Loudness is how strong or soft a sound is. It depends on how far an object vibrates from its resting spot.

🎯 Exam Tip: When defining loudness, connect it directly to the amplitude of the sound wave; greater amplitude means greater loudness.

 

Question 8. What type of sound waves does a bat, rat, and whale produced?
Answer: Bats, rats, and whales produce ultrasonic sound waves. These sounds have frequencies higher than what humans can hear, which is above 20,000 Hz.
In simple words: Bats, rats, and whales make sounds that are too high-pitched for humans to hear, called ultrasonic sounds.

🎯 Exam Tip: Remember that ultrasonic sounds are used by these animals for echolocation (navigating and finding prey) due to their high frequency and short wavelength.

 

Question 9. Write the full form of SONAR?
Answer: The full form of SONAR is **Sound Navigation and Ranging**. SONAR systems use sound waves to detect objects underwater and measure distances.
In simple words: SONAR stands for Sound Navigation and Ranging, a method that uses sound to find things underwater.

🎯 Exam Tip: Know the full form and basic application of SONAR, particularly its use in underwater detection.

 

Question 10. What is the frequency of a wave whose time period is 0.05 second?
Answer:
Frequency is defined as the inverse of the time period. This means it is the wave's cycles passing through a point in one second.
The formula is: \( \nu = \frac{1}{T} \)
Given time period \( T = 0.05 \) second.
So, Frequency \( \nu = \frac{1}{0.05} \)
Frequency \( \nu = 20 \) Hertz.
Therefore, the wave vibrates 20 times every second.
In simple words: To find how many times a wave vibrates per second, you divide 1 by the time it takes for one full vibration. Here, it vibrates 20 times in one second.

🎯 Exam Tip: Always use the correct formula \( f = 1/T \) for calculating frequency from time period, and don't forget the unit (Hertz).

 

Question 11. Give three medical uses of ultrasound.
Answer: Three medical uses of ultrasound are:
1. It is used to break kidney stones into very small pieces, which can then pass out of the body easily. This avoids surgery. 2. It helps doctors look inside the human body to examine organs like the liver or heart without needing to cut the body open. 3. It is used to check on the development of an unborn baby inside the mother's uterus during pregnancy, providing images to ensure health.
In simple words: Ultrasound helps break kidney stones, look inside organs, and check on babies before they are born.

🎯 Exam Tip: Remember specific and distinct applications of ultrasound in medicine, highlighting how it aids diagnosis and non-invasive treatments.

 

Question 12. What is embryo death?
Answer: Embryo death refers to a tragic situation where some people illegally try to find out the gender of an unborn child during pregnancy. If they discover the infant child is a girl, they sometimes cause the termination of the pregnancy, leading to the death of the embryo or fetus. This is a severe ethical and legal issue.
In simple words: Embryo death, in this context, means ending a pregnancy if it is found that the unborn baby is a girl, which is illegal and wrong.

🎯 Exam Tip: Understand that practices like female foeticide are illegal and unethical, and awareness about this issue is important.

 

Question 14. Can SONAR technique can be used to determine the depth of the sea?
Answer: Yes, the SONAR technique can definitely be used to determine the depth of the sea. It works by sending sound waves down to the seabed and measuring the time it takes for the echo to return. The depth can then be calculated using the speed of sound in water.
In simple words: Yes, SONAR can find how deep the sea is by sending sounds and timing how long their echoes take to bounce back.

🎯 Exam Tip: Explain the principle of SONAR for depth measurement: sound waves (ultrasound) are sent, and the time taken for the echo to return is used with the speed of sound to calculate distance.

 

Question 15. How do we feel sound?
Answer: We feel sound because sound waves cause our eardrum to vibrate. These vibrations are then transmitted through the small bones in our ear and eventually send electrical signals to our brain through the ear cavity and nerves. Our brain interprets these signals as what we perceive as sound.
In simple words: Sound makes our eardrum shake. These shakes are sent to our brain, which then tells us that we are hearing something.

🎯 Exam Tip: Focus on the role of the eardrum's vibration and the transmission of signals to the brain as the core mechanism of hearing.

Sound Short Answer Type Questions

 

Question 1. The pulse rate of a man is 80 beats in one minute. Calculate its frequency.
Answer:
The pulse rate is the number of beats per unit time. We need to find the frequency, which is the number of beats per second.
Number of beats = 80
Time = 1 minute = 60 seconds
Frequency \( = \frac{\text{Number of beats}}{\text{Time in seconds}} \)
Frequency \( = \frac{80}{60} \)
Frequency \( \approx 1.33 \) Hz.
This means the man's heart beats about 1.33 times every second.
In simple words: If a man's pulse beats 80 times in one minute, then in one second, it beats about 1.33 times.

🎯 Exam Tip: Convert the time to seconds before calculating frequency, and remember that frequency is typically expressed in Hertz (Hz).

 

Question 2. Explain loudness or intensity of sound.
Answer:
Loudness is a quality of sound that helps us tell a weak (feeble) sound from a strong (loud) sound, even if they have the same frequency. It mainly depends on the amplitude of the sound wave. When a vibrating object moves with a larger amplitude, the sound produced is louder. This is because a larger amplitude means more energy is being carried by the sound wave. Also, if the surface area of the vibrating object is larger, it tends to produce a louder sound because more air is displaced.
In simple words: Loudness tells us how strong a sound is. A bigger shake (amplitude) makes a louder sound, and a bigger surface making the sound also makes it louder.

🎯 Exam Tip: Clearly link loudness to the amplitude of the vibrating body; greater amplitude means more energy and thus a louder sound.

 

Question 3. Derive a relationship between the time period and frequency of a wave.
Answer:
The time period (T) of a wave is the time needed for one complete wave or oscillation. So, if one wave is produced in T seconds.

\( \implies \) In T seconds, 1 wave is produced.

\( \implies \) Therefore, in 1 second, the number of waves produced is \( \frac{1}{T} \).
By definition, the number of waves produced in 1 second is the frequency ( \( f \) or \( \nu \) ).

\( \implies \) So, Frequency \( f = \frac{1}{T} \).
This formula shows that frequency and time period are inversely related; as one increases, the other decreases. The product of frequency and time period is always 1 ( \( f \times T = 1 \) ).
In simple words: Time period is the time for one wave. Frequency is how many waves in one second. So, frequency is 1 divided by the time period.

🎯 Exam Tip: Clearly define both terms, then logically derive the inverse relationship \( f = 1/T \) step-by-step, showing how the number of waves in one second is the inverse of the time for one wave.

 

Question 4. Distinguish between musical sound and Noise.
Answer:

Musical sound has a harmonious and predictable pattern, while noise is irregular and disruptive. This distinction is based on the regularity of their wave patterns.
In simple words: Musical sound is nice to listen to and has a regular pattern. Noise is harsh, unplanned, and does not have a clear, repeating pattern.

🎯 Exam Tip: Highlight the key differences in regularity, pleasantness, and changes in pitch/loudness to distinguish between musical sound and noise.

 

Question 5. What is noise pollution. How can we control noise pollution?
Answer:
Noise pollution is the presence of unwanted, unpleasant sounds in our environment. These sounds can come from various sources and often have a high pitch, which can be more irritating than low-pitched noise. High levels of noise can harm our ears, make us tired, and reduce our ability to concentrate. Very loud noise can even cause illness or temporary hearing loss. Common sources of noise include aircraft, moving vehicles, excessively loud music, and household appliances.

**Ways to reduce unwanted noise:**
While we cannot get rid of all noise, we can lower it to acceptable levels using these methods:
1. Install silencers on vehicles to reduce the sound they make. 2. Use sound-absorbing materials in homes, such as carpets and curtains, and plant trees between houses and roads to block sound. 3. Heavy vehicles should not be allowed in residential areas to minimize disturbance. 4. Ban the use of loudspeakers for social or religious events, or strictly control their volume. 5. Factories should be located far away from residential zones. 6. Play televisions, radios, and music systems at home at low volumes.
In simple words: Noise pollution is bad, loud sounds that harm our ears and focus. We can lessen it by making machines quieter, using sound barriers like trees, keeping noisy vehicles away from homes, stopping loud loudspeakers, building factories far from houses, and playing music softly.

🎯 Exam Tip: Ensure your definition of noise pollution is clear, and provide a comprehensive list of control measures that are practical and impactful.

Sound Long Answer Type Questions

 

Question 1. Di Processing math: 100% oundness and Pitch.
Answer:
Loudness and Pitch are two important characteristics that help us describe sound.

Understanding both loudness and pitch is key to describing the full quality of any sound we hear. They are distinct properties that help characterize sounds in various contexts.
In simple words: Loudness is about how strong a sound feels to our ears and depends on how big the sound wave is. Pitch is about how high or low a sound is, and it depends on how fast the sound wave vibrates.

🎯 Exam Tip: Create clear distinctions between loudness (linked to amplitude and intensity) and pitch (linked to frequency), providing examples for each characteristic.

 

Question 2. Which object is vibrating when the following sounds are produced?
(a) The sound of a sitar or veena.
(b) The sound of the tabla.
(c) The sound of a school bell
(d) The buzzing of bee or a mosquito.
(e) The sound of a bursting balloon
(f) The radio.
Answer:
(a) For a sitar or veena, the **strings** vibrate to create sound. (b) For a tabla, the **skin (membrane)** stretched over the drum vibrates to produce sound. (c) For a school bell, the **metal disc** of the bell vibrates when struck by a hammer, making sound. (d) For a buzzing bee or a mosquito, their **wings** vibrate very quickly to produce the buzzing sound. (e) For a bursting balloon, the **air** inside the balloon vibrates suddenly and then the rapid outward movement of air vibrates, creating the sound. (f) In a radio, the **speakers** (specifically the diaphragm inside the speaker) vibrate to produce sound. These vibrations are then transmitted through the air to our ears.
In simple words: Sound is made when something moves back and forth quickly. For instruments like sitar, strings shake. For drums, the skin shakes. For bells, the metal shakes. Bees use their wings. A bursting balloon makes air shake. A radio's speakers shake to make sound.

🎯 Exam Tip: For each item, clearly identify the specific part of the object that vibrates to produce the sound, demonstrating an understanding of the source of vibration.

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