# Does the refractive index law change according to the medium

1. Mar 11, 2015

### Syndy

The refrative index law should be sine(i)/sine(r) but in the answer he done the opposite. I included the answer in the bottom of the question.

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2. Mar 11, 2015

### Staff: Mentor

It just depends on what you call i and r and which angle you know.

You can also write it as $\sin(\alpha) n_\alpha = \sin(\beta) n_\beta$ where nα means the refractive index of the medium where you have the angle α and similar for β. Usually, one medium is air with n=1.

3. Mar 11, 2015

### Syndy

In the question provided, the i angle is the one from the lamp in the water and the r is the one in the air.

What do you think about the answer I attached? Why is the r angle is the one in the water?!

4. Mar 11, 2015

### Staff: Mentor

As I said, it does not matter how you call them, you just have to be consistent. n refers to the water, so the sine in the denominator on the other side should use the angle in the water here.

5. Mar 11, 2015

### Syndy

Ok. Thank you very much.