Question

State two conditions for an echo to be heard?

Answer 1

The two conditions are: It distance between the reflector and the source should be 17 m And the 2nd condition should be that the reflector should not absorb the sound become it will not produce any echo

Answer 2

The conditions are :-

 1. The minimum dist. between source and reflecting surface must be 17.2 m. 

2. The tym interval between the orignal and the reflected sound must be 0.1 sec.

3. The reflecting object must be bigger then the wavelength of the sound.