Two solid spheres of radius r made of the same type of steel are placed in contact. the magnitude of the gravitational force they exert on each other is f1. when two other solid spheres of radius 3r made of this steel are placed in contact, what is the magnitude of the grav force that they exert on each other?
a) f1
b) 3f1
c) 9f1
d) 81f1

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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