Which statement is true about the amount of refraction of light waves as they pass through a material, or medium? Depends on the angle at which the wave strikes the medium
Increases with an increase in density of medium
Decreases with an increase in density of medium
Depends on the temperature of the light wave

Working alone at its constant rate, pump x pumped out ¼ of the water in a tank in 2 hours. then pumps y and z started working and the three pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 3 hours. if pump y, working alone at its constant rate, would have taken 18 hours to pump out the rest of the water, how many hours would it have taken pump z, working alone at its constant rate, to pump out all of the water that was pumped out of the tank? a) 6b) 12c) 15d) 18e) 24