How are bats able to avoid obstacles in their way?
Answer
Bats emit the high frequencies that range between 20 KHz to 75 KHz. The echoes from these sounds help in locating the obstacles in their path and to avoid them.
A person fires a gun and other boy at a distance hears the sound of the fire $2.5 s$ after seeing the flash. If the speed of sound in air is $330 ms^{-1}$, find the distance between the boys.
Answer
Distance between boys = speed of sound x time taken to reach sound
$= 330 x 2.5 = 825m$
The time interval between a lighting flash and the first sound of thunder was found to be 6 s . If the speed of sound in air is 330 $ms ^{-1}$, find the distance of the flash from the observer.
Answer
The distance of the flash from the observer = speed in air x time taken for the first sound to reach
$330 \times 6=1980 m$
How do the following factor affect the speed of sound in air? Moisture in air.
Answer
The speed of sound increase with an increase in humidity because the moisture in air decrease the density of air and the speed of air is inversely proportional to the density of air. Hence, the sound travels faster in moist air.
he sound of an explosion on the surface of a lake is heard by a boatman 120 m away and by a diver 120 m below the point of explosion. Out of the two persons, who would hear the sound first? Why?
Answer
The diver will hear the sound first because the sound travels faster in water than in air.
How does the speed of sound in air vary with the temperature?
Answer
The speed of sound in air increases with increase in temperature because with increase in temperature, the density of air gases decreases and speed of air is inversely proportional to density of air.
On placing your ear close to an iron railing which is tapped some distance away, sound is heard twice. Explain, why?
Answer
The sound produced by the moving wheels of the train travels faster on the iron track than in the air. So, firstly sound produced because of railway track is heard and then heard in the air.