A girl is sitting in the middle of a park of dimension 12 m × 12 m. On the left side of it there is a building adjoining the park and on right side of the park, there is a road adjoining the park. A sound is produced on the road by a cracker. Is it possible for the girl to hear the echo of this sound? Explain your answer.
ScienceClass 9CBSEAnswered 27 Mar 2026
Answer
Soln:
Echo can be heard if the gap between the original sound and reflected sound received by the listener is around 0.1 sec.
Sound Velocity× time interval
=344×0.1
= 34.4 m
Here sound reflects from the building and then reaches the girl which is much smaller than the required distance. Hence echo cannot be heard.
Suggested Q&A
Science · Class 9- ScienceClass 91. Why does the temperature of a substance remain constant during its melting point or boiling point?
- ScienceClass 9Comment on the following statements: (a) Evaporation produces cooling. (b) Rate of evaporation of an aqueous solution decreases with increase in humidity. Sponge though compressible is a solid.
- ScienceClass 9You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. What steps would you take to dry it faster?
- ScienceClass 9It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon clothes respectively. Who do you think would be more comfortable and why?
- ScienceClass 9Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment
- ScienceClass 9Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.