# Homework Help: Refraction through slab

1. Feb 3, 2012

### sparkle123

Please see attached. I tried drawing ray diagrams but I don't know how to see the answer intuitively. It seems that there is a relatively simple qualitative proof. Also the angle of incidence is unclear and I think that the direction of the shift depends on this angle.

Thanks!

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2. Feb 4, 2012

### I like Serena

Hey sparkle123!

For instance in this article (figure 14) you can see a picture of the effect of a plane glass plate on a ray.
The ray is shifted laterally to a parallel ray.
The only effect of angle is the amount that it is shifted.
As for the direction, that depends in which way the glass is tilted.

Two parallel rays that initiate from the lines on the paper will pass the glass plate and will afterward still be parallel with the same distance between them.

3. Feb 4, 2012

### sparkle123

Thanks I like Serena!
The answer is (b) unfortunately. I think this is because the slab is at an angle.

4. Feb 5, 2012

### ehild

It is true that the image shifts to the left in case of the arrangement shown in the picture.

The problem says that the lines are closely spaced. This suggests that the light rays arriving at the eye from the lines are parallel. The angles of incidence are the same from both lines, and so are the angles of reflection. The spacing between the image lines should be the same as the real spacing. (See picture on the left.)

In case the lines are far away, the angles of incidence of the rays emerging from the lines and reaching the eye can be considerably different, and then the spacing between the images is different (larger) from the real distance. (Picture on the right)

ehild

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5. Feb 5, 2012

### sparkle123

Thanks ehild! :)