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Location of prey by bats : 

Bats can produce and detect the sound of very high frequency up to 10kHz. The sound produced by bats get reflected back from an obstacle in front of it. These echoes tell the bat how they must turn in the air to avoid collision with obstacles. By using their ears, the bats, can fly skilfully at night in the utter darkness of caves. The highly sensitive nose of a bat acts as a recorder and picks up air vibrations set in motion by the movements of other animals. It appears that the nose and ears of the bats are important factors in the radar like operation.

Resonance : “is a special case of forced vibrations. When the frequency of an externally applied periodic force on a body is equal to its natural frequency, the body readily begins to vibrate with an increased amplitude. This phenomenon is called resonance.” 

Two conditions of resonance : 

1. The natural frequency of the given body (non-vibrating body) must be equal to (or its integral multiple) the frequency of the vibrating body. 

2. The vibrating body must have sufficient force, so as to. set the other body into vibrations.

The vibrations caused by the movement of the piston, the frame of motorbike may have frequency (natural) be equal to the frequency of piston and due to resonance, it vibrates violently at that particular speed.

When note of some particular frequency is played its frequency may have matched the natural frequency of odd piece of cutlery and due to resonance the piece starts vibrating. 

While crossing the bridge when soldiers march in steps, each soldier exerts a periodic force in same phase and therefore the bridge executes the forced vibrations of frequency equal to the frequency of their steps. Now the natural frequency of the bridge happens to be equal to the frequency of the steps, the bridge will vibrate with a large amplitude due to resonance and bridge may collapse. So, the soldiers are advised to break their steps while crossing the bridge.

The nature of sound waves in air is longitudinal waves.

Tuning fork is the device which is used for producing sound in laboratory experiments.

The speed of sound is lower than that of the speed of light and therefore sound reaches him later than light.

Vocal cords in our voice box produces sound

Yes, eardrum.

Correct option is D) no object

Correct Answer is: (c) 2c/3 

γ = 1 + 2/f = 1 + 2/6 = 4/3

C = √(3p/ρ) and v = √(γp/ρ)

∴ v/c = √γ/3 = √4/9 =2/3.

Given: s = 40m, v = 330 m/s

To Find: time (t)

Formula: Time = distance \(\frac{distance}{speed}\)

Calculation:

The distance travelled by the sound wave

= 2 × distance from man to wall.

= 2 × 40 = 80 m.

From formula,

∴ Time taken to travel the distance

\(\frac{distance}{speed}=\frac{80}{30}\) = 0.24 s

In the experiment to show that a medium is necessary for propagation of , sound, as the quantity of air inside the bell jar decreases, the level of ringing sound heard outside decreases.

1. It happens due to resonance. When a vehicle is driven, the piston of the engine makes in and out motion at a frequency depending upon its speed. The vibrations caused by the movement of piston are transmitted to all parts of the vehicle. It is just possible that some parts of the vehicle (or its frame), may have natural frequency of to and fro movement of piston at the certain speed of the vehicle. When this happens, then at this particular speed of the vehicle that part starts vibrating vigorously due to resonance. 

2. To stop the rattling sound. The speed of vehicle is changed, so that the condition of resonance will not then hold.

Correct Answer is:(b) T_A - 4T_B 

Let n = frequency of tuning fork,

l = length of each string,

m = mass per unit length of each string

n = 1/2l √T_A/m = 2 x 1/2l √T_B/m.

Correct Answer is: (a) 1/4

Correct option is D) amplitude

The correct answer is b) the number of complete vibrations per second

B. solids only 

Sound does not need any material medium to travel.

The branch of physics which deals with the study of production, transmission and reception of sound is called acoustics.

Correct option is A) Frequency

Correct option is B) Vibration

A larger bell has a low resonant frequency and the sound is able to travel more distance and is louder.

Measures for preventing noise pollution:

1. As far as possible, we should avoid blowing horns. 

2. The volume of the TV or radio in the house should be restricted to those watching the programmes. 

3. Vehicles should be maintained properly to reduce the unnecessary sounds they produce. 

4. Factories, airports, railway stations and bus stands should be located at the proper distance away from residential area. 

5. Planting of trees helps reduce noise as trees act as a natural barrier.

The reason behind the creation of noise is vibrating objects.

Planting trees along roadside is helpful because

1. Plants reduce noise pollution.

2. Plants reduce air pollution.

1. Sound is generated due to the vibration of an object, e.g. bell, string or diaphragm of a musical instrument.

2. Vibrations are imparted to the molecules in the air. These vibrations reach our ears through the air and sound is heard.

3. Vibrations of an object is necessary for generation of sound.

4. These vibrations in air are called travelling longitudinal waves which we can hear.

1. Loudness 

2. Pitch 

3. Quality or Timbre 

1. Loudness: 

• It is defined as the characteristic of a sound that enables us to distinguish a weak or feeble sound from a loud sound. 
• The loudness of a sound depends on its amplitude. 
• Higher the amplitude louder will be the sound and vice-versa. 
• When a drum is softly beaten, a weak sound is produced. However, when it is beaten strongly, a loud sound is produced.
• The unit of loudness of sound is decibel (dB).

2. Pitch: 

• The pitch is the characteristic of sound that enables us to distinguish between a flat sound and a shrill sound. 
• Higher the frequency of sound, higher will be the pitch. High pitch adds shrillness to a sound. 
• The sound produced by a whistle, a bell, a flute and a violin are high pitch sounds.

3. Quality or Timbre: 

• The quality or timbre is the characteristic of sound that enables us to distinguish between two sounds that have the same pitch and amplitude
• For example in an orchestra, the sounds produced by some musical instruments may have the same pitch and loudness.

(i) True.

(ii) False. (In Jaltarang, the frequency of sound produced depends on the height of the air column inside the glass cup; the more the height of the air column, the less is the frequency of the sound produced.)

Sound is a form of energy which produces sensation of hearing in our ears.

Loudness defines how loud a sound is to a listener. 

Intensity is a measure of the energy contained in a wave. Its unit is decibel(dB).

Vibration is a rapid, to and from periodic motion of an object about its mean position.

Compressions: The particles are closest to each other in this. The density of the medium is maximum at compression. 

Rarefaction: The particles are farthest from each other. The density of the medium is minimum for rarefaction.

There are two types of mechanical wave.

1. Transverse wave

2. Longitudinal wave

1. Transverse wave: 

• The particles of the medium vibrate in a direction, which is perpendicular to the direction of propagation of the wave. 
• E.g. Waves in strings, light waves, etc. 
• Transverse waves are produced only in solids and liquids.

2. Longitudinal wave: 

• The particles of the medium vibrate in a direction, which is parallel to the direction of propagation of the wave.
•  E.g. Waves in springs, sound waves in a medium. 
• Longitudinal waves are produced in solids, liquids and also in gases.