Question

the brightness of the illumination of an object varies inversely as the square of the distance from the object to the source of light. how far from the bulb does an object receive four times as much illumination as it does when it is 8 m from the bulb

Answer 1

I=k/d^2

4=k/d^2 and 1=k/64  so if we divide the first by the second we get:

4/1=(k/d^2)/(k/64)

4=(k/d^2)*(64/k)

4=64/d^2

d^2=64/4

d^2=16

d=4 meters