Question

The intensity, 1, of light varies inversely as the square of the distance, d2 from the light source. If 1 is 30 units when d is 6 meters, find 1 when d is 3 meters

Answer 1

The intensity of light will be 120 units.

Explanation:

If the intensity of light varies inversely as the square of the distance, it means that if the distance increases x times, the intensity of light will decrease x^2 times (and if the distance decreases x times, the intensity will increase x^2 times).

When the distance is equal to 6 meters, the intensity of light is 30 units. Then, the new distance is 3 meters, that is, the old distance has decreased by 6/3 = 2 times.

So, the intensity of light will increase by 2^2 = 4 times:

New intensity = Old intensity * 4 = 30 * 4 = 120 units