Question

The intensity 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 is 45 w/m^2 when the distance is 5 m. find the intensity when the distance from the light bulb is 7 m away

Answer 1

Answer:

I(7)   =  22.96 W/m²

Step-by-step explanation:

Let intensity of light, be  I(d)   where d is distance. There must be a proportionality factor K such as

I(d)  = K /d²

Now for d = 5 m    I(d)  =  K* 1/d²

then  45 * 25 = K

K =  1125

To find the intensity when the distance from the light bulb is 7 m away

I(7)   =  K / 49

I(7)   =  1125/49   W/m²

I(7)   =  22.96 W/m²