Question

The intensity I of light from a light​ bulb, measured in watts per square meter ​(w/m squared​), varies inversely as the square of the distance d from the light bulb. Suppose I is 70 ​w/m squared when the distance is 3 m. Find the intensity when the distance from the light bulb is 2 m away.?

Answer 1

Answer:

$157.5W/m^2$

Explanation:

We are given that

$I=70w/m^2$

When d=3 m

We have to find the intensity when the distance from the light bulb is 2 m away.

According to question

Intensity,$I\propto\frac{1}{d^2}$

$I=\frac{kd^2}$

Where k=Proportionality constant.

Substitute the values

$70=\frac{k}{3^2}$

$k=70\times 3^2=630$

Intensity when d=2 m

$I=\frac{630}{2^2}=157.5W/m^2$