(a) You detect a sound level of 97 dB when you are 3m from a sound source. Calculate the power of the source. Assume it emits sound in all directions...

(a)

You detect a sound level of 97 dB when you are 3m

from a sound source. Calculate the power of the

source. Assume it emits sound in

all directions uniformly.  

(b)

How far do you need to be from the source

so that you can barely hear any sound?

(c)  How much energy goes into your ear in 4 seconds

when you are 2 m from the source. Assume that the

radius of the opening into your ear is 0.4 cm.

(d) Periodic waves on the sea move at a speed of 4 m/s.

A boat floating on the sea takes 2.5 seconds to move

from its highest point to its lowest point.  Calculate the distance between two adjacent crests (high points

of the wave).