# Oxford PAT 2015, Question 14

## 4 thoughts on “Oxford PAT 2015, Question 14”

1. jason says:

it doesnt say any thing about the value of index of reflection in the question. I am wrong if I draw angle of incidence < angle of refraction.

1. No that’s fine, you can draw the angle of incidence greater than or less than the angle of refraction (in fact it would be OK to draw them the same angle but for clarity I probably wouldn’t advise it).

2. rob says:

In the diagram above you have drawn theta 1 on the other side of the ray to the way I did it. Surely this makes the answer then cos theta 1 >n2/n1?

thanks

1. Hi Rob, thanks for your comment.

Yes your reasoning is correct (because you have drawn an angle which is pi/2 minus my angle). But the ‘angle of incidence’ is a technical term with a specific meaning: it’s the angle between the incident ray and the line perpendicular to the surface of the material that the ray is entering. So the angle you have drawn isn’t the angle of incidence.