a.
The intensity of a wave (I) at a surface is equal to :
I = P / A
Where:
P = power output of the speaker = 1 w
A= surface area of the speaker = 0.05 m2
I = 1 w / 0.05m^2 = 20 w/m^2
b.
The intensity at a distance r from the speaker is found by:
I = P / (4πr^2)
Solve for r:
[tex]r=\sqrt[]{\frac{P}{4\pi I}}[/tex][tex]r=\sqrt[]{\frac{1W}{4\pi(0.1w/m^2)^{}}}[/tex]r=0.892 m
