View Full Version : Mirrors and Reflections

2005-Dec-20, 09:16 PM
Hello, my first post so bear with me! I think this question is to do with 'light' so I hope it is acceptable in an Astronomy/Space forum.

If you placed two mirrors directly in front of each other you end up with a 'tunnel' of reflections so to speak. Is the appearance of each reflection anything to do with the speed of light? ie is the image reflecting back and forth at the speed of light? If so, what happens when you remove one mirror, is the image (light) not still travelling (somewhere)?

Not sure if I am making sense but any comments are appreciated.


Dragon Star
2005-Dec-20, 09:23 PM
Ok, I will take a poke at it, thought I may be off and someone else can clear it up for you.

Ok, the reflection between the mirrors are traveling at the speed of light, back and forth between the mirrors, light travels in straight lines, unless acted upon on other ways (the warping of space time, but thats a different story), so when you remove one mirror the light indeed travels in a straight line in the direction you point it in.

And welcome to the Fourm! Hope you enjoy your stay.

2005-Dec-21, 08:08 AM
Only the light reflects.

The images are illusions constructed in a brain of an observer who intercepts some of the light.

Ken G
2005-Dec-21, 08:52 AM
You can imagine a similar experiment with infinitely many mirrors, laid out next to each other with each one a little farther than the last, such that you can see an infinite number of smaller and smaller images of yourself, but the images are side-by-side instead of embedded. There's no multiple reflections then, you just have a bunch of independent mirrors. But since they are farther and farther away, you can fit an infinite number in your visual field (let's say each is twice as far as the last). Note that you can ask a very similar question here, when you step in front of those mirrors, what happens? Well, each mirror can only bounce light from your face after the time it takes light to go from your face to that mirror and back, so the farther and farther mirrors will take longer and longer to show your image. In principle, you could see your image sequentially appearing on them, but in practice it all happens too fast.
In this sense, the image is "travelling", and so is the light, but if you remove the mirrors then the light that hasn't bounced yet never does. The light that has bounced would show a mirror that isn't there any more, like stars that we can see that may have gone supernova already.