# Homework Help: Focus moonlight wth a mirror system

1. Dec 20, 2006

Well, I'm new in town and I have a serious problem. Read the story and then tell me if its possible:

In a open spot of a forest, a kid sees a sparkle from a 150 meters Manson's window. The house is located 5 meters above the forest floor level and the open spot 1-2 meters from the floor level. The sparkle comes from a mirror in the 2nd floor of the house (5 + (3+1) m aproxim. above the forest level). Can the mirror be positioned so that the moonlight that enters the house's roof can B seen in the florest's clean spot? And without moving the mirror, can the moonlight focus on it always in the same way, every full moonlight (for example by a secondary sistem of mirrors instaled on the roof?)

Thx a lot

2. Dec 20, 2006

### Hootenanny

Staff Emeritus
Hi mad sh4rk and welcome to the forums,

It would be much appreciated in future if you would use the template as provided when submitting homework problems;

3. Dec 20, 2006

### Staff: Mentor

Yeah, what Hootenanny said. Plus in this case, if you could make a sketch of the problem, that would help a lot. Try to make it easy for us to help you. (And often doing that work helps you figure out the problem yourself anyway!)

4. Dec 20, 2006

### Staff: Mentor

Oh, and I deleted your duplicate post in the Astronomy forum. Do not multiple-post questions. This is a homework problem, and belongs here in a homework forum, and should have been posted using the homework template. Now please show us your work so we can help you.

5. Dec 20, 2006

Im trully sorry bout the duplicate message.
Ive got here a scheme of the problem, made by me. I hope it helps you in helping me :p
Don't forget to read the main text of the problem in the upper of the 1st page of this post, ok? Thx

#### Attached Files:

• ###### Moonlight problem1.jpg
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6. Dec 20, 2006

### Staff: Mentor

I think the answers are yes and no, but I honestly don't completely grasp the problem statement. It seems like once the main mirror is fixed to reflect for one month's full moon, that the movement of other months' full moon overhead will not be lined up in a way that is conducive to getting it back lined up for the main reflector.

What do you know about how the moon moves in the sky month-by-month? How will the arcs of full moons over the house vary by month? What kind of secondary mirror system do you have in mind?

7. Dec 21, 2006

I don't know much about it. I know that moon position in the sky (as stars) is variable, so the mirror must B positioned in diferent angles according to the moon's positioning.

If the moon is at the left of the house, the mirror must B pointing more to the left side, the same happening with the right-sided moonlight. If the moon is behind the house, the only option is flipping the mirror to a horizontal state. If the moon is above the forest (in front of the house) the mirror must flip more towards its vertical position.

About the secondary mirror system in the roof, I wanted it to B a moonlight magnifier and simultaneously, that it could make the moonlight beam that enters the roof hole to incise the mirror always in the same way. If this was possible, the main mirror would'nt have to be oriented according to the moonlight position, as the secondary mirror system would make the light to "achieve" the mirror at the same exact point.

8. Dec 22, 2006