Answer fast
Q. Raja and Ridhi went to hill station. On a hilly area Raja shouted Ridhi's name. To his surprise he could hear same sound twice. Ridhi explained that it was echo of his own sound. On coming back to hotel, he shouted again but could not hear the echo.
a) What is echo?
b) Why could he not hear any echo in room?
c) What value was shown by Ridhi?