# The net deviation of ray A(Figure(i))) in counter clockwise direction after one reflection and emerg

1. Oct 13, 2014

### Eddie10

1. The problem statement, all variables and given/known data
The net deviation of ray A(Figure(i))) in counter clockwise direction after one reflection and emergence is 180+2i-4r (True False)

2. Relevant equations

3. The attempt at a solution
I don't know how to begin to solve this problem, so there is no attempt at a solution.

2. Oct 13, 2014

### haruspex

The 'relevant equations' section is where you can post any standard equations from theory that you believe may be relevant. Equations only related to the specific question belong in the problem statement.
Even if you don't understand how to start on the problem, you surely have some thoughts about it that you can share. This helps us understand where/why you are stuck. E.g., do you understand what is meant by a net deviation?

3. Oct 13, 2014

### Eddie10

2. Relevant equations:

Snell's Law isall i have for relevant equations.
n_1 sintheta = n_2 sin_theta

4. Oct 13, 2014

### haruspex

Ok, but that won't help here. It is purely a matter of geometry.
You didn't answer my question: do you understand what is meant by net deviation? Start with something simple - what is the deviation of the ray, in counterclockwise sense, at the internal reflection step?

5. Oct 13, 2014

### Eddie10

Ohhh....I don't understand what is meant by net deviation. What exactly is it in relation to this problem?

6. Oct 13, 2014

### haruspex

If something changes the direction of a ray the ray is said to have been deviated. The extent of the deviation is the angle (measured anticlockwise) by which the direction has changed. So if a ray strikes a mirror along the normal it will be deviated 180 degrees. If it strikes it at 30 degrees to the normal it will be deviated by either 120 degrees or 240 degrees.
After a sequence of deviations, the net deviation is the overall change in direction.
So, can you figure out the deviation that results from the internal reflection in the diagram?

7. Oct 13, 2014

### Eddie10

Alright, so this mean that the internal deviation is the path the ray originally took, and thus, it has deviated in the same direction, but counter clockwise.
So, then it can't be a 360 degree deviation, right?

Sorry, I'm still studying this topic.

Alright, so if a ray strikes at 30 degrees to the normal, how is it deviated 120 or 240 degrees?

8. Oct 13, 2014

### haruspex

Suppose the ray starts left to right at 30 degrees above the horizontal and strikes a vertical mirror. The reflection will go right to left, still at 30 degrees above horizontal. If you take the path of the ray as it is about hit the mirror and rotate it anticlockwise until it matches the path just after reflection from the mirror, what angle do you rotate the ray by?

9. Oct 13, 2014

### Eddie10

Thanks for the help. I know the answers are true for all of them, or at least I think so they're true, but I still need to go through this problem to understand what is going on.

I'll post later on in the day as I have a Physics 103 lab that I need to get ready for.