Class 8 Science Chapter 11 Important Question Answers - Sound

Q1: What is sound, and why is it important in our lives?
Ans: Sound is a form of energy produced by vibrations. It is important as it helps us communicate, and we experience various sounds in our surroundings.

Q2: Explain how a vibrating object produces sound. Give examples of musical instruments and their vibrating parts.
Ans: A vibrating object produces sound by creating compressions and rarefactions in the surrounding medium. Examples of vibrating parts in musical instruments include strings in a guitar and air columns in a flute.

Q3: How is sound produced by humans? Describe the role of the voice box in sound production.
Ans: Sound in humans is produced by the voice box or larynx. The vocal cords vibrate when air passes through them, creating sound. Muscles can adjust the tension of vocal cords to change the pitch and quality of sound.

Q4: Why does sound require a medium to propagate? Explain the concept of a vacuum and how it affects sound transmission.
Ans: Sound needs a medium to travel because it relies on the vibration of particles in the medium. A vacuum, where there is no air, does not allow sound to travel because there are no particles to vibrate and carry the sound.

Q5: Can sound travel through liquids and solids? Provide examples and explanations.
Ans: Yes, sound can travel through both liquids and solids. It can travel through water, which is a liquid, and through materials like wood and metal, which are solids.

Q6: How do we hear sound through our ears? Explain the role of the eardrum in the process.
Ans: Sound enters the ear and travels down the ear canal to the eardrum. The eardrum vibrates in response to sound, and these vibrations are transmitted to the inner ear and then to the brain, allowing us to hear.

Q7: Define amplitude, time period, and frequency of vibration. How are they related to sound?
Ans: Amplitude is the extent of vibration, time period is the time taken for one complete vibration, and frequency is the number of vibrations per second. These properties are related to the loudness and pitch of sound.

Q8: Explain how amplitude affects the loudness of sound. Provide examples.
Ans: The amplitude of vibration determines the loudness of sound. When amplitude is large, the sound is loud, as in the case of a loudspeaker. When it's small, the sound is feeble, like a whisper.

Q9: Describe the relationship between frequency and pitch in sound. Provide real-life examples.
Ans: Frequency determines the pitch of sound. Higher frequencies result in higher-pitched sounds, such as a whistle. Lower frequencies produce lower-pitched sounds, like the roar of a lion.

Q10: What is the range of audible frequencies for the human ear, and why can't we hear sounds below or above this range?
Ans: The human ear can hear frequencies roughly between 20 Hz and 20,000 Hz. Sounds below 20 Hz (infrasound) and above 20,000 Hz (ultrasound) are inaudible to us because our ears cannot detect them.

Q11: Differentiate between noise and musical sound. Provide examples of each.
Ans: Noise is an unpleasant, random sound, such as construction noise. Musical sound is pleasing and harmonious, like that produced by musical instruments.

Q12: What is noise pollution, and what are its major sources? Give examples of noise-producing activities at home.
Ans: Noise pollution is the presence of excessive or unwanted sounds in the environment. Major sources include vehicle sounds, explosions, machines, and loudspeakers. Home sources may include high-volume televisions and kitchen appliances.

Q13: What are the harms of noise pollution on human health? Explain.
Ans: Noise pollution can lead to health problems like lack of sleep, hypertension, anxiety, and hearing impairment, both temporary and permanent.

Q14: How can noise pollution be controlled? Provide measures to limit noise pollution in residential areas.
Ans: To control noise pollution, silencing devices should be installed in machinery, noisy operations should be conducted away from residential areas, and people should minimize the use of loud appliances and horns. Planting trees can also help reduce noise.

Q15: Why is it important to address noise pollution in society, and what steps can individuals take to contribute to noise reduction?
Ans: Addressing noise pollution is crucial for the well-being of individuals and the environment. Individuals can contribute by using appliances at lower volumes, avoiding unnecessary horn use, and supporting noise reduction initiatives in their communities.