Question

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?

Answer 1

Intensity of wave is defined as the work per unit area and it is calculated through the equation,
                                   I = P / A

If a person moved farther from the light source, the area covered by the light. With the equation, A is a inversely proportional to light. If the distance is to cover half of the team. The answer therefore, the intensity of the wave is lessened. 

Answer 2

It has decreased by a factor of four