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

`157.5W/m^2`

Step-by-step 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(1)/(d^2)`

`I=\frac{kd^2}`

Where k=Proportionality constant.

Substitute the values

`70=(k)/(3^2)`

`k=70* 3^2=630`

Intensity when d=2 m

`I=(630)/(2^2)=157.5W/m^2`