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Given: n₀ = 350 Hz, v = 340 m/s,

n_A = 370 Hz

To find: Speed (v_L), Frequency (n_A)

Formulae:

i. When the car moves towards the stationary source then,

n_A = n₀ \((\frac{v+v_s}{v})\)

ii. When the car moves away from the stationary source then,

n_A = n₀ \((\frac{v-v_L}{v})\)

Calculation: From formula (i),

370 = 350 \((\frac{340+v_L}{340})\)

∴ 359.43 =340 + v_L

∴ v_L = 19.43 m/s

From formula (ii),

∴ n_A = 350 \((\frac{340-20}{340})\) = \(\frac{35}{34}\) × 320

∴ n_A = 329.41 Hz

Correct option is B) C

Correct option is D) D

Correct option is C) stringed instrument

Correct option is B) Larynx

Sound is a form of energy. A vibrating body produces sound.

A honeybee can’t make a sound using vocal cords. The buzzing sound that you b*ear from any flying insect is caused by vibration of their wings when flying.

Frequency is expressed in hertz

(c) time period

(c) Percussion

Vibrations in a body produce sound

(c) (iii) and (iv)

Vibration means a kind of rapid to and fro motion of an object.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

False 

Explanation: 

wavelength of ultrasound = 5 MHz 

velocity of ultrasound = 1540 ms^-1 

Then, for sound wave

Velocity (u) = Wavelength (λ) \(\times\) frequency(f)

⇒ frequency(f) = \(\frac{velocity}{wavelength}\) = \(\frac{1540}{5 \times 10^6}\) = 3.08 \(\times\) 10^-4m =0.03 mm

a. correct

b. false, when frequency decreases pitch decreases

Agree. Bats can produce and hear ultrasonic waves. The sound they produced reflects by hitting on objects. The bats can analyze the returning sounds.

• Air horn
• Loudspeaker
• The sounds of vehicles etc

t = 2s, ν = 332 m/s, s = ?

Required distance

s = \(\frac{vt}{2}\) = \(\frac{332\times 2}{2}\) = 332m

False 

Explanation: 

The total distance covered by the sound from the point of generation and reflecting surface and back should be at least (344 m/s) x0.1 s = 34.4 m. Thus, the minimum distance between point of generation and reflecting surface should be half of it i.e. 17.2 m.

The number of vibrations produced by a vibrating body in one second is called frequency

The repetition of the sound, which is reflected from a high building or any such object is called an echo.

False 

Explanation: 

The speed of sound decreases as we go from solid to the gaseous state. Thus, sound travels faster in water than in air.

Correct Answer is: (a) 1.22v

Tension ∝ extension, and speed ∝ √tension.

Correct Answer is: (c) F

Slogans to reduce sound pollution:

1. The more you make noise. The faster you lose your voice. 

2. Noise an evil. You help doing it, it gives you a reward making you a deaf.

True 

Explanation: The speed of sound depends on the properties of a medium. It travels faster at a higher temperature than at a lower temperature.

The following measures which can be taken to reduce noise pollution caused by traffic from reaching the residents of the area: 

1. The residential area must be declared as no use of horns. 

2. The colonies must be established at a distance than the roads.

Ways of reducing noise pollution : 

1. Factories should be located far away from residential areas. 

2. Heavy vehicles should not be allowed in residential areas. 

3. At homes T.V. radio, power music system, should played at a low volume. 

4. Machines should be designed in such a way, so that they produce minimum noise.

Condition for resonance:

Resonance occurs when the frequency of the applied force is exactly equal to the natural frequency of the vibrating body.

1. Attach silencers to bikes and other machines to reduce sounds. 

2. Manufacture machines that work with less noise. 

3. During the use of TV and tape recorder tune down volume of sound. 

4. Plant trees to reduce sound pollution. 

5. Community laws must. Silence zones near school/colleges, hospitals, etc.

6. Noise producing industries, airports, bus and transport terminals and railway stations to sighted far from living places.

Resonance is a special case of forced vibrations, when frequency of the driving force is equal to the natural frequency of the body.

Harmful effects of sound pollution : 

1. Noise produces headaches, irritatibility and nervous tension. 

2. A long exposure to noise pollution may result in the loss of hearing to deafness. 

3. Noise in the surroundings interferes with the conversation with another. 

4. It causes anger, tension and interferer with the sleep pattern of individuals

Completed table:

a. 5 

b. 5 

c. 20

Slogans to reduce sound pollution:

1. The more you make noise. The faster you lose your voice. 

2. Noise an evil. You help doing it, it gives you a reward making you a deaf.

Effects of sound pollution on biodiversity:

1. The first harmful effect is loss of hearing. 

2. It also leads to several health related problems, e.g: Sleeplessness, hypertension, increase in blood pressure, etc. 

3. It effects the mental health of people. 

4. In animals, noise can increase the risk of death by altering predator or prey detection and avoidance, interfere with reproduction and navigation and contribute to permanent hearing loss. 

5. Noise pollution causes poor quality of crops.

6. Under water animals such as whales and dolphins too experience discomfort due to noise pollution caused by submarines, shipping companies and sonars. Cuttle fish and octopus suffer serious damage from noise pollution.

The people having damage to hereby birth effect many difficulties for communication, for ability to speak, vulnerability to danger, etc.

• Causes mental stress.
• Causes emotional strain
• Causes deafness
• Increase the blood pressure

• Ban the air horn
• Control loudspeakers
• Use silencers in vehicles
• Control the sound having more than 50 dB near the hospitals

No. We cannot hear the sound having a frequency greater than 20000Hz

1. It is extensively used in medical applications like sonogram. 

2. It is also employed in dishwashers.

Use in SONAR

To find out the disease and treatment in medical field

A. sound will be louder but pitch will not be different 

In the second case sound will be louder but pitch will not be different.