# Assertion and Reason Questions for Class 9 Science Chapter 12 Sound

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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.

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

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.

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.

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.

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.

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.

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