### Home > PC3 > Chapter 10 > Lesson 10.1.4 > Problem10-84

10-84.

The amount of illumination $A$ from a light source is inversely proportional to the square of the distance $d$ from the source.

1. Express $A$ as a function of $d$.

$A(d)=\frac{k}{d^2}$

2. If the distance from a light source is tripled, what happens to the amount of illumination?

$A(3d)=\frac{k}{(3d)^2}$