NCERT Solutions for Class 9 Science Chapter 12: Sound

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The NCERT Solutions for Class 9 Science Chapter 12 Sound are provided in this article below. Some of the important concepts of Class 9 Science Chapter 12 Sound are:

Difference Between Echo and Reverberation
Structure of Human Ear
Sonar

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NCERT Solutions for Class 9 Science Chapter 3

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Important Topics for Class 9 Science Chapter 12 Sound

A sound is a vibration that propagates through a medium in the form of a mechanical wave. The medium in which it propagates can either be a solid, a liquid or a gas. Sound travels fastest in solids, relatively slower in liquids and slowest in gases. Sound moves through a medium by alternately expanding and contracting the parts of the medium which it is traveling through.

Diference Between Echo and Reverberation

Echo occurs due to the spontaneous reflection of sound from various surfaces, including walls, furniture, and other similar objects. However, Reverberation porpagates via air due to multiple reflections of sound waves from different surfaces like walls, furniture and more.’

Example: The formation of_______ is found to occur when the reflecting surface is 17m.

Echoes
Noise
Sound
Reverberation

Solution: Option 1 is the correct answer as because echoes are known to cause when certain reflecting surfaces are at a distance greater than 17m and more.

Structure of Human Ear

Human ear is known to include three parts, namely the outer ear, middle ear and inner ear. Ideally, the ear canal situated upon the outer ear is found separated from the tympanic cavity located in the middle ear by the eardrum.

Example: Highlight the function of hearing.

Solution: Hearing is the basic function of the human ear. It basically works towards identiffying and interpreting sounds in our surroundings. The ears further helps to send electrical signals to the brain, assisting the brain to perceive and comprehend the sound. The sequential process of identifying, analysing and decoding sound waves is known as hearing.

Sonar

Sonar is an abbreviation of “Sound Navigation and Ranging.” Sonar is basically a navigation system which identifies and uses acoustic signals to recognize distant underwater communications.

Sonar technologies can be further classified into two segments:

Active Sonar
Passive Sonar

Also Read:

Chapter Related Links
Intensity of Sound	Frequency and Wavelength	Unit of Vibration
Sound Important Questions	Ear Ossicles	Inaudible and Audible Sound
Sound Waves	Reflection of Waves	Loudness of Sound

Also Check:

Important Science Study Guides
Physics Constants	Difference between in chemistry	Difference between in biology
Named Reactions	Difference between in physics	Periodic Table

CBSE X Related Questions

1.
Assertion (A): Reflex actions do not involve thinking.
Reason (R): Most reflex actions are controlled by the spinal cord.
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
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2.
Given below is a pyramid showing various trophic levels in an ecosystem:
(a) From the organisms listed below, identify which one is to be placed at which trophic level:
Deer, Grass, Lion, Snake, Rabbit
(b) Discuss the reason why primary consumers will have more energy as compared to secondary consumers?
(c) Why is the base of the pyramid broad?
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3.
What is the function of diaphragm in human respiratory system ? Where is it present in human body ?
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4.
Draw a neat diagram to show germination of pollen on the female reproductive part of the flower. Name and label only the following parts:
(a) The part that receives the pollen grain.
(b) The structure that carries the male germ cell to reach the female germ cell.
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5.
Which structure in a leaf is mainly responsible for gaseous exchange?
- Xylem
- Stomata
- Phloem
- Cuticle
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6.
From the given situations, identify 'Chemotropic' and 'Geotropic' movements in parts of plants, respectively:
(i) Growth of pollen tube towards ovule.
(ii) Movement of sunflower towards sunlight.
(iii) Movement of root towards Earth/Gravity.
(iv) Movement of leaves due to breeze.
- (i) and (iii) respectively
- (iii) and (i) respectively
- (i), (ii) and (iii), (iv) respectively
- (i), (iii) and (ii), (iv) respectively
View Solution