00:01
In this problem, we're considering an aquarium with a fish who has swum, this is my fish, so that they are at a distance of 20 centimeters from the front of the tank.
00:17
We're told that the tank is 35 centimeters wide, which means our fish is 15 centimeters from the back of the tank.
00:28
And we're told that we are observing from the front of the tank and that there's a mirror on the back of the tank.
00:38
In part a, we want to know what is the apparent distance from the front wall of the aquarium to the fish.
00:48
And so it might be tempting to say that distance is 20 centimeters because the fish is 20 centimeters away from the front wall.
00:57
But due to refraction, the fish is actually going to appear closer.
01:04
And so we can figure out that apparent distance using the relationship that, excuse me, if you're looking into water, the index of refraction for water over the index of refraction for air is going to be equal to the actual distance over the apparent.
01:27
Distance.
01:29
So that means that the apparent distance for something that's being refracted is equal to the actual distance times the index of refraction for air over the index of refraction for water.
01:42
Our actual distance is 20 centimeters...