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##### Question: 1

##### Answer: 1

1-47##### Question: 2

##### Answer: 2

2-47##### Question: 3

##### Answer: 3

3-47**Part (A)**

**Reflecion of sound:**

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

**Example: **

When we clap or shout near a reflection surface such as tall building or a mountain, we hear the

Same sound again a little later.This sound which we hear is called an echo and is a result of reflection of sound from the surface.

**Explanation**:

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

**Part (B)**

**Given data:**

Frequency (f) =512Hz

Speed of sound (v)= 140ms-1

Wavelength of sound **(λ)=?**

**Solution**

** We know that; v = f λ**

**
v/f = λ**

**
λ =v/f**

**putting given values :**

**
λ = 140/512**

** λ = 0.273m**

** **

**
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** **

##### Question: 4

##### Answer: 4

4-47**Part (A)**

**Longitudinal Waves:**

**Nature of sound:**

**Wavelength:**

**Part (B)**

**Given data:**

**Solution:**

##### Question: 5

##### Answer: 5

5-47This wave which do not require medium for their propagation are called electromagnetic waves example: X rays light waves heat waves

##### Question: 6

##### Answer: 6

6-47This law state that the force needed to compress or streched the spring by some distance is directly proportional to the distance: f*-x _____ f= kx

The force is basically restoring force where k is spring constant which is measure of stiffness of spring so it tell us the nature of spring.

##### Question: 7

##### Answer: 7

7-47The distance between the two consective crest or through is called wavelength it is represented by greek symbol lamda.

##### Question: 8

##### Answer: 8

8-47Wave motion is basically the propagation of disturbances produced by the source in equal intervals time during wave motion waves transport energy from one point to other e.g energy transported by water waves.

##### Question: 9

##### Answer: 9

9-47A compression is region in longitudinal wave where the particles of medium are closest together.

Compressed spring portion producing compression.

##### Question: 10

##### Answer: 10

10-47A simple pendulum is simple harmonic oscillator that has small massed bob suspended from light string of length m .

Time period is given by: **t **=** π l/g**

##### Question: 11

##### Answer: 11

11-47One complete round trip of vibrating body about its mean position is caused one vibration.

The maximum displacement of vibrating body on each side from mean position .

##### Question: 12

##### Answer: 12

12-47Vibration: One complete round trip of vibrating about its mean position is called one vibration.

Frequency: The number of vibration or cydes of a vibrating body in one second is called frequency it Is reciprocal of time period f = 1/1

Amplitude: The maximum displacement of vibrating body on either side from its mean position is caused its amplitude.

##### Question: 13

##### Answer: 13

13-47Ripple tank is a device used to produce water waves and to demonstrate different properties of water waves like reflection refraction and diffraction.

##### Question: 14

##### Answer: 14

14-47When an object oscillates about fixed position such that its acceleration is directly proportional to its displacement from mean position and always directed toward mean position its motion is caused is SHM

A & -x

There must be elastic restoring force acting on system the acceleration of system should be directly proportional to displacement and always directed toward mean position.

##### Question: 15

##### Answer: 15

15-47The bending or spreading of wave around sharp edges or corner of obstacles or slits is called

diffraction.

##### Question: 16

##### Answer: 16

16-47The wave is disturbance in the medium which causes the particle of medium the undergo vibratory motion about their mean position is equal intervals of time.

Types:

Mechanical waves:

The waves which require any medium for their propagation are called mechanical waves e.g

Water waves , sound waves

Electromagnetic waves:

The waves which require any medium for their propagation are called mechanical waves e.g

Water waves ,sound waves

##### Question: 17

##### Answer: 17

17-47The wave moving in one direction in medium and fall on the surface of other medium they bounce back into the first medium such that the angle of incidence to the angle of reflection.

< i= <r

##### Question: 18

##### Answer: 18

18-47The waves which require the medium for their propagation are called mechanical waves .

Types:

Longitudinal waves:

In longitudinal waves the particle of medium move back and forth along the direction of waves e.g

Waves produced in slinky spring by to and for motion.

Transverse waves:

In transverse waves the vibratory motion of particles of medium is perpendicular to the direction of propagation of waves e.g waves on surface of water.

##### Question: 19

##### Answer: 19

19-47The time period of simple pendulum given by: t = 2 **π** l/g

If length is doubled l= 2l

T = 2 **π** 2l/g

T = 2 **π** (2) l/g

T = (2) 2 **π** l/g

T = 1.44 2 **π** l/g

Hence the time period increases 1.44 times.

##### Question: 20

##### Answer: 20

20-47The waves in which the particle of medium move back and forth along the direction of propagation of waves the wave has compression and rare fraction e.g the wave produced in slinky spring sound waves

Transverse waves:

The waves in which the vibratory motion of particles of medium is perpendicular to the direction of propagation of wave.e.g water waves and light waves.

Plane waves in ripple tank under go refraction when they move from deep to shallow water what##### Question: 21

##### Answer: 21

21-47In ripple tank the frequency of wave is constant and directly varies with frequency of vibrator but frequency of wave is constant and speed varies and wave length when the water wave enters the shallow region from deep region wave length decreases so apeed also decreases.

##### Question: 22

##### Answer: 22

22-47Crest: The part of wave above the mean position is called crest.

##### Question: 23

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23-47The time taken by vibrating body to complete one vibration is called time period

T = I/f

##### Question: 24

##### Answer: 24

24-47The equation which explains the motion of the waves in terms of its speed is known as wave equation

The speed of wave given by :

V = distance/time = s/t

As s Is the distance = wavelength

Time interval t = I = time period, so

V = i/t

As f = i/i

So, v =fr

##### Question: 25

##### Answer: 25

25-47When the sound travel in given medium its strikes the surface of another medium and bounce back in some direction this phenomena is called reflection of sound this process is also known as echo.

##### Question: 26

##### Answer: 26

26-47When the waves moving in one medium fall on the surface of another medium they bounce back into the first medium such that angle of incidence <I should equal t angle of reflection <r

<i=<r

##### Question: 27

##### Answer: 27

27-47The waves which do not require any material medium for their propagation are caused electromagnetic waves e.g xrays, light ways.

##### Question: 28

##### Answer: 28

28-47Vibration or oscillation is repeated back and
forth motion along the same path. Vibrations occur in the vicinity of a point
of stable equilibrium. An equilibrium points is a point at which the net force
acting on the body is zero . An equilibrium point is also called stable point when at small displacements from it the net force pushes the body back to the equilibrium point. Such a force is called a restoring force since it tends to restore equilibrium. Consider a bowl and ball example under stable equilibrium condition. When ball is displaced from its equilibrium position, it will start moving under restoring force towards equilibrium position, opposite to the displacement `x' . After reaching equilibrium position the object will continue under inertia and will reach the other extreme position and thus it will continue to oscillate back and forth. Simple Harmonic motion

##### Question: 29

##### Answer: 29

29-47_{res}is directly proportional to the displacement x from equilibrium position.

_{res}α-x

_{res}= -kx

_{res}= ma

_{res}=-kx and F

_{res}= ma we get

##### Question: 30

##### Answer: 30

30-47_{res}is directly proportional to the displacement x from equilibrium position.

_{res}α-x

_{res}= -kx

_{res}= ma

_{res}=-kx and F

_{res}= ma we get

##### Question: 31

##### Answer: 31

31-47_{rest}= -mgsin0 eq (1)

_{rest}= -mgx/l eq 3

_{rest}= ma eq (4)

##### Question: 32

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32-47##### Question: 33

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33-47##### Question: 34

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34-47##### Question: 35

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35-47##### Question: 36

##### Answer: 36

36-47- Initially the mass m is at rest at mean position O thus its KE and P.E both are zero
- When the mass m is pulled from mean position O to extreme position A its P.E become maximum at A.
- Now from position A when mass m is reached it tend to move towards mean position O. Now at mean position K.E becomes maximum and P.E becomes zero.
- Due to inertia "m" does not stop at mean position "O" and continues its mean position towards extreme position B, thus when mass "m" moves from O to B its K.E decreases and P.E increases. At position B, K.E becomes zero and P.E becomes maximum.

##### Question: 37

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37-47##### Question: 38

##### Answer: 38

38-47- Bob at mean position: in the equilibrium the mean position O, the net force on the bob is zero and the bob is stationary.
- Motion of bob from extreme position: if we bring the bob to extremes position A , the net force is not zero

##### Question: 39

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39-47##### Question: 40

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40-47##### Question: 41

##### Answer: 41

41-47- Longitudinal waves
- Transverse waves