When we wil through the ball upward which wave produce?
Answers
When you drop a stone in, it pushes some of the water out of the way, making a hole. And, because water is very difficult to compress, it also produces a hump where the pushed out water went. So part of the water will try to move up to level it out, and part will try to move down. Each will move back to the level point. But they won't stop accelerating until they reach level, by which time they are travelling too fast to stop, so they overshoot. Which is going to produce an up-and down motion. But that is no reason for that up and down motion to stay in one place - there is nothing tying it. In fact, every point tries to spread out uniformly. But they are all in a circle. So the bits that spread out round the centre cancel out the next door bits. The bits that spread in towards the centre produce an up-and-down that stays put. But the bits that spread our away from the centre have nothing to stop them. So they produce a circular wave that spreads away from the centre. Since it is getting bigger and bigger, it gets shallower and shallower, until we can no longer see it.