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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: bec on February 05, 2008, 06:19:12 pm

Title: Infinitely reflecting pairs of mirrors
Post by: bec on February 05, 2008, 06:19:12 pm
Hi everyone

I don't do physics but i need to know for art how mirrors positioned in particular ways can reflect an image an infinite number of times, and appear to be "curving" with each repetition.

Sorry that's so inarticulate but it's hard to describe! Basically I was wondering if someone could explain to me (or link me to a website that explains) the angles at which the mirrors need to be positioned for this to occur.

Title: Re: Infinitely reflecting pairs of mirrors
Post by: abcat on February 05, 2008, 06:39:48 pm
I actually used this idea I learnt from physics in a photography project for school, using two mirrors to infinitely repeat one object in a circle, such that a viewer would struggle to pick the real object.

Basically, all that is needed is two flat rectangular mirrors placed in a V. Place the object inside the V, and the image of the object will repeat around in a circle when you look directly at the point of the V from the back. For instance, place a lego man inside the V, and the you will have an image of 20 or so lego men all facing the point in the V.

The closer the mirrors (i.e. the smaller the angle the two make), the more repeated images you get.

      /\   ________mirrors
    /    \
  /        \
/     o     \
Title: Re: Infinitely reflecting pairs of mirrors
Post by: bec on February 05, 2008, 07:12:39 pm
so since the smaller the angle between the two mirrors, the more repeated images you get, could i put an object in a box with sides made of double-sided mirrors just fractionally angled so they're not exactly parallel? the effect i'd like to get is so you can look in the box and see an infinite number of repetitions of the object so it looks like there are millions of them going back into the distance (kind of like your photog project abcat!).
do you know WHY this "phenomenon" (haha you can tell i don't know physics) occurs? is it just to do with the angles of refraction as the light bounces from one mirror to another and comes off at a different angle? It's just, I think if i understand why/how this works i could come up with a more sophisticated idea for my project.
thank you!
Title: Re: Infinitely reflecting pairs of mirrors
Post by: abcat on February 05, 2008, 09:07:03 pm
I'm not entirely clear on your box idea, perhaps a little diagram could shed some light? I gather you want the images infinitely repeating, but remember to picture it as an actual object.

------------------ mirror
          o               object
------------------  mirror

You have to be able to see one side of the mirror, yet when you look at the mirror, you are viewing the image on a 90 degree angle. If you have some small mirrors, practice to see what works. It's a lot easier to figure it out by playing around with some mirrors (any mirror will do), than to understand the theory.

But the repitition of images 'phenomenon' is a lot simpler to understand than it seems. Think of it in terms of light. Light reflects/absorbs off/into the object, the remaining colours reflecting to your eyes, which then processes it as an visible image. In the same way, this light reflects to the mirror, again, reflecting to your eyes. Some of the light from the object can again reflect from the mirror to the other mirror and to your eyes, and so on. Thus, you are not just seeing the original object, you are seeing the image from the first mirror, than the image from the second mirror, and also subsequent images reflected back and forth in the two mirrors. It's a simplistic explanation but basically it's how it works.

Glad I can be of help, it was a cool little effect that I felt made a great photo and would make a great art project.