# Finding apparent depth real depth and refractive index

1. Sep 7, 2016

### RabbitWho

1. The problem statement, all variables and given/known data
refractive index = 1.33 (water)
real depth = 10m
2. Relevant equations
refractive index = real depth divided by apparent depth

3. The attempt at a solution
I'm going to call apparent depth X

1.33 = 10/x

So I multiply 10/x by 10 so that i have x and 1.33 x 10 is 13.3... that's right, isn't it? but that makes no sense, because the apparent depth must be less than the actual depth.

I know the real answer is 7.52.. what am I doing wrong?

No idea if the problem is with my maths or my physics.

2. Sep 7, 2016

### Staff: Mentor

No, not right. If you multiply $\frac{10}{x}$ by 10 you get $\frac{100}{x}$.

You need to get that x out of the denominator, so multiply both sides by x, not 10. (Or you can cross multiply. Or you can invert both sides. Many ways to play the game!)

3. Sep 8, 2016

### RabbitWho

Thank you! that makes sense. I got the answer right now :)