Question

1. The intensity of a particular earthquake wave is measured to be 1.60 x 106 W/m2 at a distance of 40.0 km from the source. What was the intensity when it passed a point only 1.00 km from the source? Assume that earthquake waves travel uniformly in all directions W/m2 2. The team monitoring a space probe exploring the outer solar system finds that radio transmissions from the probe take 2.10 hours to reach earth. How distant (in meters) is the probe? 3. Two astronauts are 1.10 m apart in their spaceship. One speaks to the other. The conversation is transmitted to earth via electromagnetic waves. The time it takes for sound waves to travel at 320 m/s through the air between the astronauts equals the time it takes for the electromagnetic waves to travel to the earth. How far away from the earth is the spaceship?

Answer 1

I alpha 1/r^2 therefore 1.6 times 10^6/x = (1 times 10^3)^2/(40 times 10^3)^2 therefore x = 2.56 times 10^9 w/m^2 v = d/t therefore d = 3 times 10^8 times 2.10 times 60 = 3.78 times 10^10 minutes (v = 3 times 10^8 m/s) v = d/t therefore 320 = 1.10/t = 3.43 times 10^-3 s therefore 3 times 10^8 = d/3.43 times 10^-3 therefore d = 1031250 m