Question

please Help !!
The intensity I of light bulb measured in watts per square meter (w/m^2), varies inversely as the square of the distance d from the light bulb . . suppose I is 55 w/m^2 when the distance is 8 m . find the intensity when the distance from the light bulb is 5 m away

Answer 1

The first sentence tells you
\[\text{intensity}=\frac{\text{power}}{(\text{distance})^2}~~\iff~~I=\frac{P}{d^2}\]
Given that \(I=55\) when \(d=8\), you can find the corresponding value of \(P\):
\[55=\frac{P}{8^2}~~\implies~~P=\cdots\]
If the power \(P\) is kept constant, then the intensity \(I\) will still change as a function of the distance \(d\). Using this \(P\), you would then find \(I\) when \(d=5\) by solving
\[I=\frac{P}{5^2}~~\implies~~I=\cdots\]

Answer 2

oh ok