# Class 10th Physics Unit 11 Questions An Anwer

## Class 10th Physics Unit 2 Questions An Anwer on Newsongoogle By Bilal Articles

Discover in-depth Class 10th Physics Unit 2 questions and answers on Newsongoogle by Bilal Articles. Uncover valuable insights and explanations to excel in your physics studies. Trust Bilal Articles for expertly crafted content to enhance your understanding of Unit 2 concepts. Elevate your learning experience with comprehensive resources tailored for Class 10 students.

### unit 11

Q 1. What is a sound wave? How sound is produced?

Ans: Sound Wave: A sound wave is a pattern of disturbance caused by the movement of energy traveling through a medium as it propagates away from the source of the sound. Like other waves, sound is also produced by vibrating bodies. Due to the vibration of bodies, the air around them also vibrates and the air vibration produces a sensation of sound in our ears.

Q 2. What is a tuning fork?

Ans: It is a U-shaped body having two metal prongs with a stem at the bottom and used for producing sound of a particular frequency.

Q 3. Why medium is required for the propagation of sound waves?

Ans: Sound waves are compressional waves in nature. These are the types of mechanical waves and we know that mechanical waves require a medium for their propagation. So we can say material medium is necessary for the propagation of sound from one point to another. This material medium can be a gas, a liquid, or a solid.

Q 4. Define the loudness of sound and what are the factors affecting it.

Ans: Definition: “The characteristic of sound by which a loud and mint sound can be distinguished is called loudness of sound”. Factors affecting the loudness of Sound: The following are the factors that affect the loudness of sound: i. Amplitude of vibrating body ii. Area of vibrating body iii. Distance from vibrating body iv. The physical condition of ear.

Q 5. Define the pitch of the sound.

Ans: The characteristic of sound by which a shrill sound can be distinguished from a grave one is called the pitch of the sound. Dependence on Frequency: It depends upon the frequency, the greater the frequency, the higher the pitch, and the lower the frequency, the lower the pitch.

Q 6. Define the quality of sound with an example.

Ans: “The characteristic of sound by which Eco sounds of the same loudness and pitch are distinguished from each other is called the quality of sound. Example: The sound of flute and piano of given loudness and pitch can be distinguished because the quality of their notes is different Dependence: It depends upon the waveform of the sound waves. The loudness and pitch of these two sounds are the same but their waveforms are different. So their quality is different and can be distinguished from each other.

Q 7. What is the intensity of sound?

Ans: 1ntensity of sound: “Sound energy flowing per second through a unit area held perpendicular to the direction of propagation of sound waves is called the intensity of sound” Unit: The unit of intensity of sound is watt per square meter (Wm-2) Intensity is a physical quantity and can be measured accurately. Intensities of Faintest and Loudest sound: The intensity of the faintest sound is 10-12 Wm-2 and the intensity of the loudest sound, which can be heard without pain, is 1 Wm-2.

Q 8. State Weber Fechner Law.

Ans: Weber Fechner Law: It has been proved experimentally that the loudness (L) of a sound is directly proportional to the logarithm of intensity. Mathematically: L ∝ log I L = K log l Where L is the loudness of sound, K is a proportionality constant and I is the intensity of sound.

Q 9. What is Intensity Level or Sound Level?

Ans: The difference between the loudness of any unknown sound and the faintest sound (L – Lo) is called the intensity level or sound level. Mathematically: Sound level = K log Io Where ‘I’ is the intensity of the unknown sound, K is a proportionality constant and Io is the intensity of the faintest sound.

Q 10. How reflection (Echo) of sound can be defined?

Ans: Echo: When sound is incident on the surface of a medium it bounces back into the first medium. This phenomenon is called echo or reflection of sound.

Q 11. Calculate the minimum distance to hear the Echo.

Ans:The sensation of sound persists in our brain for about 0.1 s. To hear a clear echo, the time interval between our sound and the reflected sound must be at least 0.1 s. if we consider the speed of sound to be 340 runs-1at a normal temperature in air, we will hear the echo after 0.1 s. The total distance covered by the sound from the point of generation to the reflecting surface and back should be at least 340 ms-1 x 0.1 s = 34.0 m. Thus, for hearing distance echoes, the minimum distance of the obstacle from the source of sound must be half of this distance which is 17m. Echoes may be heard more than once due to successive or multiple reflections.

Q 12. What is meant by Noise Pollution and describe its Sources.

Ans: Noise Pollution: Noise pollution has become a major issue of concern in big cities. Noise is an undesirable sound that is harmful to the health of humans and other species. Sources: The Sources of noise pollution are as: i. Transportation equipment ii. Heavy machinery iii. These are the main sources of noise pollution. For example, the noise of machinery in industrial areas, loud vehicle horns, hooters, and alarms.

Q 13. What are the effects of Noise?

Ans: Effects of Noise: Noise has negative effects on human health as it can cause conditions such as i. Hearing loss ii. Sleep disturbances, iii. Aggression, iv. Hypertension, v. High stress levels. vi. Noise can also cause accidents by interfering with communication and warning signals.

Q 14. Enlist any five sounds of Music and Noise.

Ans: Musical sounds: i. Sound of Harmonium ii. Sound of birds iii. Sound of waterfall iv. Sound of violin v. Sound of flute Noises: i. Sound of traffic ii. Sound of moving train iii. Sound of aero planes iv. Sound of crying v. Sound of horns.

Q 15. What are the major sources of noise in our society?

Ans: Automobiles, airplanes, helicopters, trains, heavy machinery, heavy traffic, loudspeakers are the major sources of noise pollution in our society.

Q 16. How noise can be reduced?

Ans: Trees and different appliances are useful to reduce the noise.

Q 17. What do you know by Safe Level of Noise?

Ans: Safe Level of Noise: A safe level of noise depends on factors: the level (volume) of the noise; and the period of exposure to the noise. The level of noise recommended in most countries is usually 85-90 dB over an eight-hour workday. Noise pollution can be reduced to an acceptable level by replacing noisy machinery with environmentally friendly machinery and equipment, putting sound-reducing barriers, or using hearing protection devices.

Q 18. Define acoustics protection. Explain the importance of acoustic protection.

Ans: Acoustic Protection: The technique or method used to absorb undesirable sounds by soft and porous surfaces is called acoustic protection. Importance of Acoustic: Reflection of 5otlnd is more prominent if the surface is rigid and smooth and less if the surface is soft and irregular. Soft, porous materials, such as draperies and rugs absorb large amounts of sound energy and thus quiet echoes and softening noises. Thus by using such materials in noisy places, we can reduce the level of noise pollution.

Q 19. What is meant by Reverberation?

Ans: When sound reflects from the wall, ceiling and floor of a room, the reflecting surfaces are too reflective and the sound becomes garbled. This is due to multiple reflections called reverberations. In the design of lecture halls, auditorium or theatre halls, a balance must be achieved between reverberation and absorption. It is often advantageous to place reflective surfaces behind the stage to direct sound to the audience.

Q 20. What is audible frequency range for human and why we cannot hear if sound ranges more than this range.

Ans: A human ear can hear sound only if its frequency lies between 20 to 20000 Hz. A Human ear can neither hear a sound of frequency less than 20 Hz nor a sound of frequency more than 20000Hz. Sounds of frequency beyond the 20000 eardrum of human ear cannot vibrate so rapidly. The audible range is different for different persons and it also varies with the age.

Q 21. What is silent whistle and why it is called so?

Ans: Some people use silent whistle to call dogs whose frequency lies between 20,000 Hz to 25,000 Hz and human ear cannot detect it. so, it is silent for human that is why it is called Silent but it is not silent for the dogs because their audible range is much more than human.

Q 22. What are ultrasonic and why they are used in our life?

Ans: Sound waves of frequency higher than 20000 Hz are ultrasonic. Bns: It has been seen that ultrasonic waves care more energy than audible sound waves. Moreover, according to the relation v = λ f, the wavelength of ultrasonic waves is very small. Due to these characteristics they are usefully utilized in medical and technical fields.

Q 23. How we can find the depth of ocean?

Ans: Ultrasound is used to locate underwater depths or is used for locating objects laying deep on the ocean floor, etc. the technique is called SONAR (Sound navigation and Ranging). The sound waves are sent from a transmitter, and a receiver collects the reflected sound. The time lapse is calculated, knowing the speed of sound in water, the distance of the object from the ocean surface can be estimated.

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