Seeing the invisible Brain teasers and fun science tricks
Step 1: To do this experiment you’ll need a bowl and a coin. Place the bowl on a table in front of you and put the coin in the bowl. In this position the coin should be visible to you.
Step 2: Now push the bowl away from you until the sides of the bowl hide the coin from view. You can’t see the coin unless you lean forward, right? Or can you?
Step 3: To make the coin visible again from your position, all you need is ordinary water!
Step 4: Carefully, so the coin doesn’t get pushed out of place, pour a glass of water into the bowl. Is the coin now partly in view?
Step 5: Pour in enough water so the coin comes fully into view. The coin appears to rise together with the bottom of the bowl. What is actually happening?
Step 6: While the bowl was empty, light rays bouncing off the coin couldn’t reach your eyes. Light rays travel in straight lines, after all, and were blocked by the opaque walls of the bowl. But what changed when we added water? Light rays travelling out of the water into the air are bent (refracted), allowing them to travel over the sides of the bowl and toward your eyes. That’s the reason the bottom of the bowl appeared to rise.
Step 7: Knowledge of refraction can help you when you are swimming. In a place where the bottom is visible, don’t forget that you’re seeing it higher than it actually is–at roughly a quarter of its depth.