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Q & A: moving underwater

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Most recent answer: 11/22/2007
Q:
If you are looking at an object moving underwater at a certain speed, will it look like it is moving faster or slower when observing from above the water? Or will it look like it is moving at the same speed?
- Sabrina
Denver, CO USA
A:
Letís say youíre outside the water looking down. When the object is straight below you, it looks straight below you. When itís moved off to the side, the light rays that reach you from it bend as they leave the water. The direction of the bend is to make them head more horizontally in the air than they do in the water. So the object looks even farther away than it is. So at least in this case it looks like the object has gone farther and thus seems to be moving faster than it it really is.

Mike W.

(published on 11/22/2007)

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