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##### Question: 1

##### Answer: 1

1-50**Part (A)**

**Longitudinal Waves:**

**Nature of sound:**

**Wavelength:**

##### Question: 2

##### Answer: 2

2-50**Part (B)**

**Given data:**

##### Question: 3

##### Answer: 3

3-50**Part (A)**

The characteristic of sound through which a loud and a faint sound can be distinguished is called loudness. The loudness of sound depend upon the amplitude of the vibrating body area of vibrating body. Distance from vibrating body.

**Pitch of Sound:**

The characteristic of sound by which a shrill sound can be distinguished from a grave sound is called pitch.

**Quality of sound:**

The characteristic of sound by which two sounds of same
loudness and pitch are distinguish from each other iss called quality a sound**.**

**Example:**

If in a room a note of given loudness and pitch is sounded on flute and also on a piano, we can distinguish between them by standing even outside the room, because quality of these notes is different.

**Intensity
of sound:**

Sound energy following per second through a unit area held perpendicular to the direction of sound wave is called intensity of sound.

**Unit:**

Its unit is Walt per square meter Wm-2.It is a physical quantity and can be measured accurately.

##### Question: 4

##### Answer: 4

4-50**Part
(B)**

**Frequency = f= 2kHz**

** = 2*1000Hz**

** = 2000 Hz**

**Wavelength
=** **λ=35cm**

** = 35/100 m**

** = 0.35 m**

**Distance = s= 1.5 km **

** = 1.5*1000 m**

** =1500 m **

** Time = t=?**

**Solution:**

**We know that **

** V = f λ**

** = 2000*0.35**

** = 2000 * 35/100**

** = 20*35**

** = 700 ms1**

**We
also know that **

** S = v*t**

** 1500 = 700*t**

** T = 1500/700**

** T = 2.1s**

##### Question: 5

##### Answer: 5

5-50Sound is a form of energy that is passed from one to another in the form of long dinal waves sound is produced a vibrating body.

##### Question: 6

##### Answer: 6

6-50Tunning fork is a device that we use to produce a particular sound if we strike the tunning fro against rubber hammer the tunning fork will begin to vibrate and produced a sound by it.

##### Question: 7

##### Answer: 7

7-50Tunning fork is a device that we use to produce a particular sound if we strike the tunning fro against rubber hammer the tunning fork will begin to vibrate and produced a sound by it.

##### Question: 8

##### Answer: 8

8-50In longitudinal or compressional waves the particles of the medium vibrate parallel to the direction of propagation wave.

For example: sound wave.

##### Question: 9

##### Answer: 9

9-50Loudness is the characteristics of sound by which loud and faint sounds can be distinguished.

##### Question: 10

##### Answer: 10

10-50The maximum displacement of a vibrating body on either side from its mean position is called its amplitude.

##### Question: 11

##### Answer: 11

11-50Pitch is the characteristic sound by which we can distinguish between a shrill and a grave sound.

Quality: The characteristic of sound by which we can distinguish between two sound of same loudness and pitch is called quality.

##### Question: 12

##### Answer: 12

12-50Speed of sound in solids is more then in liquids because the solids atoms are closely packed whereas molecules of liquids are for a part.

##### Question: 13

##### Answer: 13

13-50We can recognize person speaking with some loudness from their voice because sound waves have different waves forms so their quality is different and we can distinguished them from each other.

##### Question: 14

##### Answer: 14

14-50Sound energy passing per second through a unit area held perpendicular of sound waves is called intensity of sound. the unit of intensity of sound is unit per square metre (Wm-2)

##### Question: 15

##### Answer: 15

15-50If intensity I of any unknown sound is 10 times greater than the intensity Zo of the faintest audible sound i.e I =10 I0 is called bell

Zero bell: Faintest audible sound having intensity 10-12 WM-2 is called reference intensity or zero bell

##### Question: 16

##### Answer: 16

16-50Difference (L-LO) between the loudness L of an unknown sound and the loudness Lo is called the intensity level sound level of the unknown sound.

L- Lo=10 log ( I/Io) (db)

##### Question: 17

##### Answer: 17

17-50Ultrasound is used to locate under water depths or is used for locating objects lying deep on the ocean floor etc,the techniques is called sonar the sound waves are send from a transmitter and receiver collects the reflected sound the time lopse is calculated knowing the speed of sound in water the distance of the object from the ocean surface can be estimated.

##### Question: 18

##### Answer: 18

18-50The decibel scale is a logarithmic measure of the amplitude of sound waves.

##### Question: 19

##### Answer: 19

19-50When 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 there is no difference between echo reflection of sound.

##### Question: 20

##### Answer: 20

20-50**Speed of sound at **25
**°C through bra is 4700ms-1 and through
iron is 5950ms-1.**

##### Question: 21

##### Answer: 21

21-50**Frequency is the
number of waves passing through a point in one second **

**Pitch: pitch is
characteristic of sound due to which we can distinguish between shrill and grave sound.**

##### Question: 22

##### Answer: 22

22-50**Ultrasound is useful
in medical field and higher frequency (v=fr) with very small wave lengths than
audible sound waves.**

##### Question: 23

##### Answer: 23

23-50**Loudness of sound
depends the following factors the amplitude of the vibrating body area of
vibrating body distance from vibrating body.**

##### Question: 24

##### Answer: 24

24-50**Such sounds which has
pleasant effect on our ears are called musical sounds.**

##### Question: 25

##### Answer: 25

25-50**The sound with
jarring effect on our ears are called noise.**

##### Question: 26

##### Answer: 26

26-50**The technique or
method used to absorb undesirable sound energy by soft and porous surfaces is called acoustic protection.**

##### Question: 27

##### Answer: 27

27-50**The range of the
frequencies which a human ear can hear is called the audible frequency range.**

##### Question: 28

##### Answer: 28

28-50**A normal human ear
can hear sound only if its frequency lies between 20Hz and 20,000 Hz a human ear can oscillate
back and forth up to 20,000 times in one second .**

##### Question: 29

##### Answer: 29

29-50**Since db is the unit
of sound level and its value depend upon the log of intensities therefore 50db
sound from two bodies does not constitute 100db sound each 10db increase in
sound makes the sound 10-times louder.**

##### Question: 30

##### Answer: 30

30-50##### Question: 31

##### Answer: 31

31-50##### Question: 32

##### Answer: 32

32-50##### Question: 33

##### Answer: 33

33-50^{-12}W/m

^{2}and as high as 1 W/m

^{2}(

^{12}from lowest to highest. To permit comparison of values which vary so greatly in magnitude, it is most convenient to express them in terms of their logarithms- the power to which 10 must be raised to equal the number.

^{2}, then mathematically

_{o}' represents the loudness of faintest audible sound of intensity `I

_{o}' such that I

_{o}= 10

^{-12}W/m

^{2}equation 1 can be written as :

_{o}= klogI

_{o}eq (2)

_{o}= klogI- klogI

_{o}or L-L

_{o}= K(logI-KlogI

_{o})

_{o}

_{o}eq (3)

_{o}but also on the unit intensity level. If the intensity of any sound is ten times greater then the intensity I

_{o}of the faintest audible sound (I=10 I

_{o}), then intensity level of such a sound is taken as unit called bel and value of k becomes 1.Substituting k= 1 equation 3 becomes

_{o}(bels)

##### Question: 34

##### Answer: 34

34-50##### Question: 35

##### Answer: 35

35-50##### Question: 36

##### Answer: 36

36-50##### Question: 37

##### Answer: 37

37-50##### Question: 38

##### Answer: 38

38-50##### Question: 39

##### Answer: 39

39-50##### Question: 40

##### Answer: 40

40-50##### Question: 41

##### Answer: 41

41-50- Loudness; loudness is the characteristics of sound by which loud and faint sounds can be distinguished.

- Amplitude of vibrating body: the loudness of sound varies directly with amplitude of vibrating body. The sound produced by a sitar will be loud if we pluck its wires more violently. Similarly, when we beat a drum forcefully amplitude of its membrane increases and we hear loud sound.

##### Question: 42

##### Answer: 42

42-50^{-2}, Js

^{-1}m

^{-2}

##### Question: 43

##### Answer: 43

43-50^{-1}at a normal temperature in air, we will hear the echo after 0.1 sec.

^{-1}* 0.1= 34 m.

- Arrange the pipes on a table near a wall.
- Place a clock near the open end of one of the pipes and try to hear the sound of the clock through the other pipe.
- Adjust the position of the pipes so that you can hear the sound o the clock clearly.
- Now , measure the angle of incidence and reflection and see the relationship between the angles.
- Lift the pipe on the right vertically to a small height an observe what happens.

##### Question: 44

##### Answer: 44

44-50_{l}= 5*v

_{a}

^{-1}at one atmospheric pressure and room temperature(21

^{o}C)

_{a}

_{a}= speed of sound in air

_{s}= speed of sound in solid

_{l}= speed of sound in liquid

##### Question: 45

##### Answer: 45

45-50- use the tape to measure a distance of 50 meters from the wall.
- Now clap your hands in front of the wall at a distance of 50 meters and check if you can clearly hear an echo from the wall. Make sure the echo is not coming from any other wall in the area. The time taken by the sound to travel 10 meters is the time difference between the clap and the echo.
- Now restart the clapping and start the stop watch at the first clap. Count the number of claps , and stop the clapping and the stop watch when you hear the echo of the 10th clap(say).
- Now find the average time for 10 claps. After calculating the time interval "t" between claps and using the formula S=vt, we can calculate the speed of sound.

##### Question: 46

##### Answer: 46

46-50- use the tape to measure a distance of 50 meters from the wall.
- Now clap your hands in front of the wall at a distance of 50 meters and check if you can clearly hear an echo from the wall. Make sure the echo is not coming from any other wall in the area. The time taken by the sound to travel 10 meters is the time difference between the clap and the echo.
- Now restart the clapping and start the stop watch at the first clap. Count the number of claps , and stop the clapping and the stop watch when you hear the echo of the 10th clap(say).
- Now find the average time for 10 claps. After calculating the time interval "t" between claps and using the formula S=vt, we can calculate the speed of sound.

##### Question: 47

##### Answer: 47

47-50##### Question: 48

##### Answer: 48

48-50##### Question: 49

##### Answer: 49

49-50- Young children can hear sounds of 20,000 Hz
- Old people cannot hear sounds even above 15,000 Hz