# Does reflection accompany refraction in Snell's law?

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1. Nov 28, 2015

### Seismic101

If the the angle of incidence of an incident ray is less than (or equal to) the Critical Angle, the ray is refracted, but do we still get some reflection from this same incident ray?

2. Nov 28, 2015

### Staff: Mentor

Hi Seismic101.

Reflection like you see from a train window pane at night?

3. Nov 28, 2015

### Seismic101

I am not sure. I wasn't really speaking about light although same principles apply, I guess? Please let me explain more.

In my field (O&G Exploration) we send vibrations into the Earth, and when this energy encounters the interface between Earth layers it follows Snell's Law. My question is: when the ray hits the interface at angle less than or equal to the Critical, we get refraction, but do we get some reflected rays as well?

I like the analogy you used! Thanks for the nice welcome!

4. Nov 28, 2015

### blue_leaf77

In optics, when a ray of light hits an interface between two different media, reflection will always take place except for when the incident angle is equal to the Brewster angle and the incoming polarization lies in the incident plane. Since, the wave you are dealing with is of longitudinal waves where polarization is not relevant, I presume reflection will always take place regardless of any condition of the system.

5. Nov 28, 2015

### Seismic101

The vibrations (mechanical waves) we send into the Earth can be longitudinal (particle motion in the direction of wave propagation) or transverse (particle motion is perpendicular to the direction of wave propagation).

Do you think this is true for any medium/ wave type? In other words, do you think there is a Brewster angle in the case of mechanical waves propagating through Earth layers?

Thanks for taking the time to reply.

6. Nov 28, 2015

### davenn

maybe this will help ?

cheers
Dave