Inverse Square Law questions, urgent help! Please, answer all!

Question

1. You are standing 10 meters from a light source. Then, you back away from the light source until you are 20 meters away from it. From your perspective, what has happened to the intensity of the wave?
a. It has decreased by a factor of two.
b. It has increased by a factor of two.
c. It has decreased by a factor of four.
d. It has increased by a factor of four.

2. You are standing 100 meters from an object emitting a sound of constant intensity (loudness). You walk toward the source of sound until you are 20 meters from it. From your perspective, what has happened to the intensity of the sound?
a. It has decreased by a factor of five.
b. It has increased by a factor of five.
c. It has decreased by a factor of twenty-five.
d. It has increased by a factor of twenty-five.

3. The Inverse Square Law applies to (check all that apply):
- Intensity of Sound
- Gravitational Force
- Intensity of Light
- Electric Force
- Magnetic Force

Answer 1

(1)

 

You doubled the distance, which means the intensity dropped to 1/4 of its level at 10 m.  The correct answer is (c).

 

(2)

 

You reduced the distance to 1/5 of its original value, so the intensity is increased to 5² = 25 times its original level.  The correct answer is (d).

 

(3)

 

All have inverse-square laws.