Answer:
0.14 seconds
Explanation:
The speed of light in vacuum is approximately 3.0*10^8. The distance that would be covered by the object would be equivalent to the circumference of the cross-section of the earth on the equator.
Circumference = 2*6400000 =4.02*10^7
Time = distance/speed = 4.2*10^7 / 3.0*10^8 =0.14s
To solve this problem it is necessary to apply the concepts related to intensity as a function of power and area.
Intensity is defined to be the power per unit area carried by a wave. Power is the rate at which energy is transferred by the wave. In equation form, intensity I is
The area of a sphere is given by
So replacing we have to
Since the question tells us to find the proportion when
So considering the two intensities we have to
The ratio between the two intensities would be
The power does not change therefore it remains constant, which allows summarizing the expression to
Re-arrange to find
Therefore the intensity at five times this distance from the source is