Rotating Question Curious About Astronomy? Ask an Astronomer
Lincolntown High School
Featured Classroom: Kathy Bosiak's class at Lincolnton High School in Lincolnton, North Carolina

Featured Classroom

Kathy Bosiak wrote to say: "Hope you had a great year since we have questioned you last. It is a new year and of course new questions. This one is directed right at your team."

"What would happen if you took 6 inch by 6 inch squares of one-way glass and made a cube with the reflective side toward the inside and sealed it up. Ideally, with no space inbetween the seams. Then you shine a laser pointer into the cube. Where will the light go? How long will it take to "escape" the cube, assuming in a perfect seam that it could not? Would the box glow or turn red? Just what exactly do you think would happen to the light?"

Curious team's answer: This is another great question! It sounds like something they would ask in a college physics class.

I think what you would see would depend on the angle that you shined the laser in. If you shine the laser in the flat side of the cube, so that the light was coming in perpendicular to the face, you would see the light go into the cube. Then when it crossed to the opposite face, part of the light would be reflected, and part would probably travel through. (We're not really sure how perfectly one-way glass reflects light, but we're guessing it might be like a partly silvered mirror. If light can get out for you to see, then it's not really a perfect reflector on the inside. We're not sure how much of a given light beam is reflected, and how much will pass through the glass for the "viewers" on the other side to observe.) But as long as you shined the light in perpendicular to the cube face, it would all look like a straight line. Light is reflected from mirrors at the same angle at which it hits the mirror. So if you shine a light perpendicularly on a mirror, it will come straight back at you. So all the light reflected from the opposite face will come straight back in the same direction as the light you were shining in.

Things would be more interesting if you shined the light in at an angle. For example, suppose you aimed the light at the bottom of the cube instead of the opposite face. Then the some of the light would again be reflected, but this time it would reflected onto a new cube face. Then, some of that light would be reflected in a new direction. So in this case the light will be able to reflect around the cube, and there'll be lots of laser lines inside. It might look a little like it's glowing! You would see a trail of reflections that would get steadily dimmer as light was lost to the outside, and eventually you wouldn't be able to trace the path anymore. This pattern would only last as long as you have the laser on. Light travels really really fast, so even if the laser beam had to bounce around the cube hundreds of times before it became too faint to see, there's no way you could see residual light travelling after you turned the laser off.

Return to Information and Guidelines for Teachers

Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist

This page has been accessed times since .
Last modified: November 28, 2003 3:53:49 PM

Legal questions? See our copyright, disclaimer and privacy policy.
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.

Warning: Your browser is misbehaving! This page might look ugly. (Details)