Two particles, each of mass m, are a distance d apart. To bring a third particle, with mass 2m, from far away to a resting point midway between the two particles, an external agent must do work equal to:

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

in this image, you can see solar radiation going through ocean water.

no image, but probably absorption

the answer is 100. i just did this lesson and got a 100% on it. : )

-fishtank