# Reflection at a Boundary

1. Jun 13, 2012

### physicsguy101

1. The problem statement, all variables and given/known data

At the boundary between water (n=1.33) and flint glass (n=1.66), incoming light at ~49 degrees from the normal is refracted.

Of course, I can use Snell's law to calculate the angle of refraction.

However, my question is whether any of the light at this boundary is also Reflected??

I think it would be because light reflects off both rough (diffuse reflection) and smooth surfaces, but can anybody confirm?

Thanks!

2. Relevant equations

N/A

3. The attempt at a solution

See above.

2. Jun 13, 2012

### Antiphon

I can confirm that your heuristic reasoning is incorrect. You do not know if it reflects or not unless you run through the equations.

Eyeballing the numbers there is a 50-50 chance you have no refelection.

3. Jun 13, 2012

### Yukoel

Yes in general reflection and refraction always occur in pairs much as in a transverse wave travelling on a string which is rare on its initial part and denser on the other .You get two waves when the transverse wave approaches the joint one which returns back(reflection) and the other which continues its path (refraction).Mathematically there is a reflection unless the strings are the same .(it is just an analogy).
However using polarized light one can get a refraction with no reflection at all.
Using Snell's law one can only verify whether light can be refracted or not ,if it can then what the angle is.Since the light approaches through the rarer medium (water) there is no scope of total internal reflection which is in a way a synonym for no refraction.
Correct me if I am wrong.
regards
Yukoel