# Mirror and reflection angle

1. Dec 9, 2013

### ExoP

1. The problem statement, all variables and given/known data
Hi!

I'm having a problem with one assignment and I would really need som help. The question is:

The Chandra X-ray telescope is used for observations in the 0.1-10 keV range. Focal
length is 10 m, max mirror radius is 0.6 m. What is the largest reflection angle in the optics
(assuming that both reflections are of the same size)?

2. Relevant equations

3. The attempt at a solution

I started first to find the wavelength by using the E=hc/λ formula. I got 12,4082 nm. After that, I'm stuck. Should I use a formula for concave mirrors? If yes, which one? I think that you need to place something in front of it to be able to calculate the angle. Glad if anyone could help :)

2. Dec 9, 2013

### Staff: Mentor

The telescope does not have mirrors in the same way optical telescopes use them. Wikimedia has a diagram of this.
I think this is simple geometry - the length and the radius are given, you can probably assume that the length of the mirrors is small compared to 10m. For X-rays that are parallel to the telescope axis, which deflection angle do you need per mirror?

3. Dec 9, 2013

### ExoP

I have actually no idea. From now, I only have the wavelength which I calculated, the eV range, the focal length and mirror radius. I'm stuck.. :/

4. Dec 9, 2013

### Staff: Mentor

Did you draw a sketch?
Can you solve it with a single mirror?

The wavelength is not relevant here, this is really just geometry.

5. Dec 9, 2013

6. Dec 9, 2013

### Staff: Mentor

It's hard to see the two reflections there (are there two?), but the basic idea is good.

7. Dec 10, 2013

### ExoP

Do you have any idea of the geometry, how to solve this problem maybe? :)

8. Dec 10, 2013

### Staff: Mentor

It's not rocket science...

Add angles to the sketch, find out which angles you know (and what you know about angles at mirrors), solve, done.

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9. Dec 11, 2013

### ExoP

Yes, I just don't remember that much about this since it was 4 years ago that I calculated anything similar to this. Thanks!

Last edited: Dec 11, 2013
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