Need for Pressure Wave

Q.

If amplitude of waves at distance r from a point source is A, the amplitude at a distance 2r will be

[MP PMT 1985]

1. 2A

2. A

3. A/2

4. A/4

Q.

If two waves having amplitudes 2A and A and same frequency and velocity, propagate in the same direction in the same phase, the resulting amplitude will be

[MP PET 1991; DPMT 1999]

1. A

2. 3A

3. 

4. 

Q. Two sound waves move in the same diretion in the same medium. The pressure amplitudes of the waves are equal but the wavelength of the first wave is double the second. Let the average power transmitted across a cross saection by the first wave be $P_1$ and that by the second wave be $P_2$ . Then

1. $P_1=P_2$
2. $P_1=4P_2$
3. $P_2=2P_1$
4. $P_2=4P_1$