Seema could easily hear her echo when she shouted in her schools multipurpose hall. Later she shouted in the same manner in her room at home but she was not able to hear any echo. Explain

Answer with Explanation:

Echo depends on "how sound waves are reflected back." A hard object, like the walls of the multipurpose hall, reflects sound waves well; thus, Seema could easily hear her echo. In addition to this, the walls of the hall are also smooth and this further allows the sound waves to bounce. On the other hand, soft objects like bed cushions in Seema's room absorbs sound. This prevents the sound waves from being reflected. In addition to this, the sound waves have hard time bouncing because there are many objects in Seema's room.

electrical power

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27