If the distance from a point source is doubled, by what factor does the intensity fall (assuming an inverse-square law)?

If the distance from a point source is doubled, by what factor does the intensity fall (assuming an inverse-square law)?

• A. It falls by a factor of 4
• B. It falls by a factor of 2
• C. It falls by a factor of 8
• D. It falls by a factor of 1/2

Answer: (A)