Assertion and Reason Questions for Class 9 Science Chapter 12 Sound

Here we are providing assertion reason questions for class 9 science. This article covers assertion reason questions based on Class 9 Science Chapter 12 Sound. To check the answer, click on ‘answer’ given below each question. After clicking it will expand.

Assertion and Reason Questions for Class 9 Science Chapter 12 Sound

Directions: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.

Q.1. Assertion : The flash of lightening is seen before the sound of thunder is heard.
Reason : Speed of sound is greater than speed of light.

Answer

Answer: (c)

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Q.2. Assertion : Two persons on the surface of moon cannot talk to each other.
Reason : There is no atmosphere on moon.

Answer

Answer: (a)

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Q.3. Assertion : Sound would travel faster on a hot summer day than on a cold winter day.
Reason : Velocity of sound is directly proportional to the square of its absolute temperature.

Answer

Answer: (c)

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Q.4. Assertion : Echo is produced when sound is incident on hard and polished surface.
Reason : Sound energy can be totally reflected by objects with soft and loose texture.

Answer

Answer: (c)

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Q.5. Assertion : The speed of sound in solids is maximum though their density is large.
Reason : The coefficient of elasticity of solid is large.

Answer

Answer: (a)

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Q.6. Assertion : Compression and rarefaction involve changes in density and pressure.
Reason : When particles are compressed, density of medium increases and when they are rarefied, density of medium decreases.

Answer

Answer: (a)

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Q.7. Assertion : The velocity of sound in hydrogen gas is less than the velocity of sound in oxygen gas.
Reason : The density of oxygen is more than the density of hydrogen.

Answer

Answer: (d)

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Q.8. Assertion : The velocity of sound increases with increase in humidity.
Reason : Velocity of sound does not depend upon the medium.

Answer

Answer: (c)

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Q.9. Assertion : The waves in which the individual particles ot the medium move about their mean positions in a direction perpendicular to the direction of wave propagation, is known as Transverse waves.
Reason : The loudness or softness of a sound is determined basically by its amplitude.

Answer

Answer: (b)

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Q.10. Assertion : Sound is a form of energy which produces a sensation of hearing in our ears.
Reason : When you clap, a sound is produced.

Answer

Answer: (b)

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Q.11. Assertion : The matter or substance through which sound is transmitted is called a medium
Reason : Sound moves through a medium from the point of generation to
the listener.

Answer

Answer: (b)

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Q.12. Assertion : Sound waves are characterised by the motion of particles in the medium and are called mechanical waves.
Reason : Air is the most common medium through which sound travels.

Answer

Answer: (a)

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Q.13. Assertion : The sound of the human voice is produced due to vibrations in the vocal cords.
Reason : Vibration means a kind of rapid to and fro motion of an object.

Answer

Answer: (b)

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Q.14. Assertion : Sound is a mechanical wave and needs a material medium like air, water, steel etc. for its propagation.
Reason : Sound cannot travel through vacuum.

Answer

Answer: (b)

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Q.15. Assertion : Echo is the repetition of sound due to reflection of original sound by a large and hard obstacle.
Reason : To hear a distinct echo, the time interval between the original sound and the reflected one must be atleast 0.1 sec.

Answer

Answer: (c)

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Q.16. Assertion : A wave is a disturbance that moves through a medium when the particles of the medium set neighbouring particles into motion.
Reason : A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position and produces a wave.

Answer

Answer: (a)

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Q.17. Assertion : Human ear converts pressure variations in air with audible frequencies into electric signals.
Reason : Audible sound lies in the range of 20 to 2000 Hz.

Answer

Answer: (d)

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Q.18. Assertion : Audible sound lies in the range of 20 to 200 Hz.
Reason : Infrasonic sound or Infra-sound has frequency less than 20 Hz.

Answer

Answer: (d)

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Q.19. Assertion : Sounds having more intensity and frequency are louder.
Reason : The loudness of a sound depends on Intensity and frequency.

Answer

Answer: (a)

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Q.20. Assertion : Pitch of a note depends upon its wavelength.
Reason : Sound can not travel through vacuum.

Answer

Answer: (d)

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Q.21. Assertion : Two persons on the surface of Moon cannot talk to each other.
Reason : Sound can not travel through vacuum.

Answer

Answer: (a)

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Q.22. Assertion : Ultrasound is an application of ultrasonic waves.
Reason : Sound travels fastest in steel.

Answer

Answer: (b)

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Q.23. Assertion : The particles do not travel all the way from the vibrating object to the ear.
Reason : A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position.

Answer

Answer: (b)

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Q.24. Assertion : An object moving at a speed greater than the speed of sound is said to be moving at Supersonic speed.
Reason : Sound travels Faster in solids and liquids than in air.

Answer

Answer: (b)

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Q.25. Assertion : To hear a distinct echo, the tine interval between the original sound and the reflected one must be at least 0.1 s.
Reason : The sensation of sound persists in our brain for about 0.1 s.

Answer

Answer: (a)

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Q.26. Assertion : On a rainy day sound travels slower than on a dry day.
Reason : When moisture is absent in air the density of air decreases.

Answer

Answer: (d)

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Q.27. Assertion : Transverse waves are not produced in liquids and gases.
Reason : Light waves are transverse wave.

Answer

Answer: (b)

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Q.28. Assertion : Ultrasounds can be used to detect cracks and flaws in metal blocks.
Reason : In stethoscopes the sound of the patient’s heartbeat reaches the doctor’s ears by multiple reflection of sound.

Answer

Answer: (b)

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Q.29. Assertion : The ceilings of concert halls and conference halls are made curved.
Reason : So that sound reach all parts of the hall after reflection from curved ceilings.

Answer

Answer: (a)

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Q.30. Assertion : SONAR is used underwater.
Reason : Sonar uses ultrasonic waves to measure the distance, direction and speed of underwater objects.

Answer

Answer: (a)

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Q.31. Assertion : The outer ear is called ‘pinna’.
Reason : When a compression of the medium reaches the eardrum the pressure on the outside of the membrane increases and forces the eardrum inward.

Answer

Answer: (b)

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Q.32. Assertion : Loud sound can travel a larger distance as it is associated with higher energy.
Reason : Compression is a part of a longitudinal wave in which the particles of the medium are closer to one another.

Answer

Answer: (b)

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Q.33. Assertion : With decrease in time period, frequency increases.
Reason : Time period and frequency are inversely proportional.

Answer

Answer: (a)

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Q.34. Assertion : Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the string suitably.
Reason : Frequency is adjusted.

Answer

Answer: (a)

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Q.35. Assertion : A trough is the lowest point the medium sinks to.
Reason : A crest is the highest point the medium rises to.

Answer

Answer: (b)

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Q.36. Assertion : Megaphones or loudhailers, horns, musical instruments such as trumpets and shehanais, are all designed to send sound in a particular direction without spreading it in all directions
Reason : In these instruments, a tube followed by a conical opening reflects sound successively to guide most of the sound waves from the source in the forward direction towards the audience.

Answer

Answer: (a)

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Q.37. Assertion : Ultrasound is not used in spiral tube.
Reason : Ultrasound is generally used to clean parts located in hard-to-reach places.

Answer

Answer: (d)

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Q.38. Assertion : Stethoscope is a medical instrument used for listening to sounds produced within the body, mainly in the heart or lungs.
Reason : In stethoscopes the sound of the patient’s heartbeat reaches the doctor’s ears by multiple reflection of sound.

Answer

Answer: (a)

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