The intensity of sound from a radio at a distance of 2 metres from its speaker is `1xx10^(-2) mu W//m^(2)`. The intensity at a distance of 10 meters would be

Options

A. `0.2xx10^(-2)muW//m^(2)`
B. `1xx10^(-2)muW//m^(2)`
C. `4xx10^(-4)muW//m^(2)`
D. `5xx10^(-2)muW//m^(2)`

Answer

C

Explanation

Intensity `prop(1)/(r^(2))implies(I_(2))/(I_(1))=(r_(1)^(2))/(r_(2)^(2))implies(I_(2))/(1xx10^(-2))=(2^(2))/(10^(2))=(4)/(100)`
`implies I_(2)=4xx10^(-4)muW//m^(2)`.