Question

Speed of sound in air __________ with the increase in humidity in air.
A. Decreases
B. Increases
C. Both
D. None

Answer 1

Hint:Students should try to recall the factors on which the speed of sound depends to solve this question. With the increase in humidity there is a decrease in the density of air. The decreased density changes the speed of sound in air.

Complete answer:
With the increase in humidity in air the fraction of water molecules to the oxygen molecules also increases. The water molecule is less massive as compared to the oxygen molecule and therefore the mass of air decreases thus decreasing the density of air (density is defined as the ratio of mass to volume). Lower the density of air faster is a sound speed. Therefore the speed of sound in air increases with the increase in humidity in the air.

Hence, option B is the correct answer.

Note: Keeping the point of decrease in density with increase in humidity one should implement the factors affecting the speed of sound in air. Increase in humidity decreases the density and hence increases the speed of sound in air.Moreover, humidity is defined as the amount of moisture or water droplets present in air. Density is the ratio of mass to volume.