# Sound Its Production And Propagation ICSE Class-7th Goyal Brothers Physics Solutions Chapter-6 Unit-1

Sound, Its Production And Propagation Class-7th Goyal Brothers ICSE Physics Solutions Chapter-6 (Sound) Unit-1(Sound, Its Production And Propagation). We Provide Step by Step Answers of Objectives, Fill in the blanks, Match the following, True/False, Incorrect and Correct, Question Type answers of Chapter-6 (Sound) Unit-1(Sound, Its Production And Propagation). Visit official Website for detail information about ICSE Board Class-7.

## Sound, Its Production And Propagation ICSE Class-7th Goyal Brothers Physics Solutions Chapter-6 Unit-1

 Board ICSE Class 7th Subject Physics Book Name Goyal Brothers Chapter-6 Sound Unit-1 Sound, Its Production And Propagation Topic Solution of exercise questions Session 2023-24

### OBJECTIVE QUESTIONS

Sound, Its Production And Propagation  ICSE Class-7th Goyal Brothers Physics Solutions Chapter-6 Unit-1

#### Que: A. Fill in the blanks spaces by choosing the correct words from the list given below :

List : lighting, air, amplitude, slower, tunning fork

1. The sound travels slower in liquids as compared to solids.

2. The speed of sound in air is around 332 ms–¹.

3. A U-shaped fork of steel used as a convenient source of sound in laboratory is called tunning fork.

4. The crack of thunder is heard much later than the flash of lighting during a thunderstorm.

5. With the increase in amplitude of a vibrating body, the loudness of sound increases.

#### Que: B. Statements given below are incorrect. Write the correct statements :

##### Question: 1. Sound can easily propagate through vacuum.

Answer: Sound cannot easily propagate through vacuum.

##### Question: 2. Sound travels slower in solids as compared to liquids.

Answer: Sound travels fastest in solids as compared to liquids.

##### Question: 3. During a thunder storm, the crack of thunder is heard first and then the flash of lighting is seen.

Answer: During a thunder storm, the crack of thunder is seen first and then the flash of lighting is seen.

##### Question: 4. When the sound travels in air, the particles of air vibrate differently compared to the vibrations of the vibrating body.

Answer: When the sound travels in air, the particles of air vibrate differently compared to the vibrations of the vibrating body.

##### Question: 5. Material medium is not necessary for the transmission of sound.

Answer: Material medium is not necessary for the propagation of sound.

#### Que: C. Write ‘True’ or ‘False’ for the following statements :

 Statements True/False 1. Sound travels fastest in metals. T 2. A material medium is not necessary for the propagation of sound. T 3. Red Indians can find out whether an enemy is approaching their camp by putting their ear to the ground. F 4. The speed of sound can be calculated is we know the distance between the source of sound and observer and the temperature of air. F 5. We cannot hear on moon, because their is no gas to propagate sound. T

#### Que: D. Tick (√) the most appropriate answer :

##### 1. An electric bell is suspended in a bell jar and then air is removed from it. On switching on the electric bell, the sound heard is :

(a) Very loud

(b) Normal sound

(c) Weak sound

(d) No sound is heard

Answer: option (d) No sound is heard is correct.

##### 2. The convenient instrument used in laboratory to produce pure sound is :

(a) Whistle

(b) Drum

(c) Tuning fork

(d) Guitar

Answer: option (c) Tuning fork is correct.

##### 3. The crack of a thunder cloud is heard later than the flash of lightning because, the light travels :

(a) Much slower than sound

(b) Much faster than sound

(c) At the same speed as sound

(d) None of these

Answer: option (b) Much faster than sound is correct.

##### 4. The approximate speed of sound in air at room temperature is :

(a) 33.2 ms–¹

(b) 3320 ms–¹

(c) 3.32 ms–¹

(d) 332 ms–¹

Answer: option (d) 332 ms–¹ is correct.

##### 5. An observer puts ear on a railway line 500 m from a friend with a hammer. When his friend hits the railway line with the hammer, the observer hears two sounds. The sound is first heard through :

(a) Railway line

(b) Air

(c) At the same time through railway line and air

(d) No sound is heard

Answer: option (a) Railway line is correct.

#### Que: E. Match the statements in Column A, with those in Column B :

 Column A Column B 1. A device used as a convenient source of sound in laboratory. (a) 5100 2. The motion of the particles of a medium about their mean positions. (b) 1500 3. A medium through which sound cannot pass. (c) Vibration 4. Approximate speed of sound in steel at room temperature. (d) Tuning fork 5. Approximate speed of sound in water at room temperature. (e) Vacuum

 Column A Column B 1. A device used as a convenient source of sound in laboratory. (a) Tuning fork 2. The motion of the particles of a medium about their mean positions. (b) Vibration 3. A medium through which sound cannot pass. (c) Vacuum 4. Approximate speed of sound in steel at room temperature. (d) 5100 5. Approximate speed of sound in water at room temperature. (e) 1500

### STUDY QUESTIONS

Sound, Its Production And Propagation  ICSE Class-7th Goyal Brothers Physics Solutions Chapter-6 Unit-1

#### Question: 1. What causes the sound? Describe an experiment in support of your answer.

Answer: Sound is produced when an object vibrates, creating a pressure wave. This pressure wave causes particles in the surrounding medium (air, water, or solid) to have vibrational motion. Vibration caused in a tuning fork makes sound and if it is dipped in water, we can see waves which proves that vibrations produce sound.

#### Question: 2. (a) What are conditions for the transmission of sound?

Answer: An object that creates vibration by striking it, secondly that body which vibrates on striking and last medium through which sound waves can travel because when an object strikes the vibrating body then vibrations are produced that develops sound waves.

#### (b) Describe sound as a longitudinal wave.

Answer: A longitudinal wave is one where all the particles of the medium (such as gas, liquid or solid) vibrate in the same direction as the wave.

#### Question: 3. Describe how the energy is carried to the ear, from the source of sound, through a material medium.

Answer: The vibrations produced by the objects reach until the eardrum through the air. These vibrations produced to make the eardrum vibrate.  And then the vibrations are passed to the inner ear through middle ear bones or ossicles.

#### Question: 4. Describe an experiment to prove that sound can transmit (a) solids (b) liquids.

Answer: (a) Solids : Tie a knot or match-stick at each end of the thread so that the thread does not slip out through the holes. This makes a toy -telephone . Now use the toy telephone as shown in figure and talk to your friend . You will be able to hear the sound of your friend.

(b) liquids : First, bring water to a deep bowl. then take two large metal coins. Then hold these two coins with both hands. (one coin per hand) Dip your hand into the water in the bowl containing the coin. Clap your hands as if moving through the water to make the coins collide. When coins collide, they make a clicking sound. This experiment proves that sound waves can travel through liquids.

#### Question: 5. Why can the sound not travel through vacuum? Describe an experiment in support of your answer.

Answer: We know a vacuum is an empty space where no matter particles are present. Sound cannot travel through a vacuum as there are no particles present for vibrations to take place.

#### Question: 6. If you are provided with a powerful cracker, a stop watch, a measuring tape and a friend to help you, explain how can you measure the approximate speed of sound.

Answer: Once you see the flash of explosion of cracker, start the stop watch. Once you hear the sound of explosion of cracker, stop the stop watch. Now you have the time taken by sound to cover 100 m. So the velocity of sound will be simply distance divided by time.

#### Question: 7. Name two source of sound. How sound is produces by human beings?

Answer: The speech box, also known as the larynx, is used by humans to create sound. The voice box is located at the top of the windpipe in our throat. The vocal cords are two ligaments found in the human voice box. The waves of the vocal cords produce sound.

— : end of Sound Its Production And Propagation ICSE Class-7th Goyal Brothers Physics Solutions Chapter-6 Unit-1:–-