How does the surface of a refracting prism become reflective?

[Browntown]

Homework Statement

How does the surface of a refracting prism become reflective?

Relevant Equations

None

In my physics lab, we placed a mirror in front of a telescope with built in crosshairs and crosshairs that were shining out the front of the telescope which reflected against the mirror and allowed us to see them and then adjust the level of the telescope until the two were aligned. Later we had to do the same but with the surface of a refracting prism where once the telescope was pointed at a specific angle, the surface became like a mirror and allowed us to align the crosshairs.

In order to fill in the theory section I need to understand how this occurs but I have no idea other than there is some kind of total internal reflection happening.

Any help understanding would be much appreciated, thank you.

 

[Anachronist]

...Later we had to do the same but with the surface of a refracting prism where once the telescope was pointed at a specific angle, the surface became like a mirror and allowed us to align the crosshairs. In order to fill in the theory section I need to understand how this occurs...

Maybe this Wikipedia article will help: https://en.wikipedia.org/wiki/Total_internal_reflection

 

[jtbell]

Yes, total internal reflection is the name of this phenomenon. Most intro physics textbooks and optics textbooks discuss it. A Google search turns up lots of results, for example:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/totint.html
At incoming angles less than the critical angle (where total internal reflection begins) you have partial internal reflection.