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# Class 9 FRANK Solutions Physics Chapter 7 - Sound - Production and Propagation of Sound

Study better with Frank Solutions for ICSE Class 9 Physics Chapter 7 Sound – Production and Propagation of Sound. Discover the properties of sound by understanding whether it can travel through vacuum and various mediums. With TopperLearning’s solutions, learn about the impact of temperature on sound.

With the ICSE Class 9 Physics chapter solutions, learn to calculate distance between two elements based on the speed of sound. For a comprehensive revision, check out TopperLearning’s videos, Selina solutions, online practice tests, and other e-learning resources.

## Sound - Production and Propagation of Sound Exercise 278

### Solution 1

Yes, Sound is form of energy.

### Solution 2

Sound is produced by the vibrating objects.

### Solution 3

No, sound cannot travel through vacuum.

### Solution 4

Yes, sound can propagate through solids and liquids.

### Solution 5

No, sound cannot be produced in vacuum. It needs a material medium.

### Solution 6

Speed of sound depends on the density, pressure, temperature, humidity and Wind.

### Solution 7

330m/s is the value of speed in air at N.T.P

### Solution 8

In water, speed of sound is 4.5 times more than that in air. And, in iron, the speed of sound is 15 times as fast in air.

### Solution 9

The speed of sound is more in the humid air as compared to dry air. Because, the air moisture decreases the density of air and speed of sound is inversely proportional to density of air. So, sound travels faster in humid air.

### Solution 10

Speed of sound does not depend on the amplitude and wavelength.

### Solution 11

The sound produced by the moving wheels of the train travels faster on the iron track than in the air. So, firstly sound produced because of railway track is heard and then heard in the air.

### Solution 12

The waves in the air causes sound . Through waves , energy get transferred from one place to another and hence the sound.

### Solution 13

The ratio of speed of light to the speed of sound is 9.1 x 105 .

### Solution 14

Speed  of sound in air is independent of variation of pressure.

### Solution 15

The speed of sound in air increases with increase in temperature because with increase in temperature, the density of air gases decreases and speed of air is inversely proportional to density of air.

### Solution 16

The diver will hear the sound first because the sound travels faster in water than in air.

### Solution 17

The simple experiment that a person can do to calculate the speed of sound in air is that a person stands at a known distance (d meter) from the cliff and fires a pistol and simultaneously start the stop watch. He stops the stop-watch as soon as he hears a echo. The distance travelled by the sound during the time (t) seconds is 2d.
So, speed of sound = distance travelled / time taken = 2d/t

### Solution 18

(i) Moisture in Air :: The speed of sound increase with increase in humidity because the moisture in air decrease the density of air and speed of air is inversely proportional to density of air. Hence , the sound travels faster in moist air.
(ii) Pressure in air:: Speed of sound is independent of the air pressure.
(iii) The speed of sound increases with the increase in temperature of the gas.

### Solution 19

The distance of flash from the observer = speed in air x time taken for the first sound to reach
330 x 6 = 1980m

### Solution 20

Distance between boys = speed of sound x time taken to reach sound
= 330 x 2.5 = 825m