Question

According to the inverse square law of light, if you double your distance to a source, the brightness will...
a. decrease by a factor of 3.
b. decrease by a factor of 4.
c. decrease by a factor of 5.
d. decrease by a factor of 6.

Answer 1

Answer:

a. decrease by a factor of 3.

Explanation:

The intensity of light is inversely proportional to the square of distance.

I ∝1/d^2

or

I= k/d^2

where k is a constant

so, if d becomes 2d , I will be come I/4

Therefore, intensity will a. decrease by a factor of 3.

Answer 2

Answer:

option (b)

Explanation:

According to the inverse square law,

$Brightness \alpha \frac{1}{distance^{2}}$

As the distance is doubles, the brightness becomes one fourth.

It means the brightness decreases by a factor of 4.

Option (b)