Posts Tagged ‘Mirror’

Convex Mirror Magic

Edit: Oh nos! I forgot to publish my post…until now.

So after my last orchestra concert ever (tears), I fell asleep on the ride home. Of course, since I don’t have a driver’s license yet, this was not a problem. : )

I didn’t wake up until we entered the parking lot and the first thing I found myself looking into was one of those round convex mirrors. The parking lot mirrors are very similar to the rear view mirrors on a car.

Because both are convex, the images created are virtual, smaller than the original object, and upright. Since everything appears smaller, it allows us to see a wider field of view than a plane mirror would. Which is of course extremely useful at times.

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CandyMirage.jpg picture by xtaintedwatersx

The Mirage® is a very special device consisting of two parabolic mirrors (the top mirror has a hole in the middle) with the concave sides facing each other. The mirrors have identical focal lengths and the Mirage® is constructed so that the focal point of a mirror coincides with the center of the other mirror (in the case of the top mirror, right where the hole is.)

Mirage.jpg picture by xtaintedwatersx

Light rays from the object at the bottom of the Mirage® will reflect off of the top mirror and travel in a parallel path. Then, after the rays hit and reflect off of the bottom mirror, they will travel towards the focal point of the bottom mirror. Which of course just so happens to be at the center of the top mirror where the hole is! So you end up with a really cool ‘real’ image even though you can’t actually touch it. Amazing!

StrawberryMirage.jpg picture by xtaintedwatersx

Strawberry M&Ms. Rawr. Pics courtesy of Gizmodo.

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I wear hard contact lenses so its no big surprise to me that if you’re close enough, a concave mirror will magnify the pores on your face and your eyeballs.

magnifyingmirror.jpg picture by xtaintedwatersx

To magnify your image in a concave mirror, you must place yourself within the mirror’s focal point.  Using a ray diagram, you would see that this clearly results in a upright, larger, and virtual image.  Which you can of course see in the mirror.  Yay.  Watch my guest Mr. Penguin from Kinetic Books: Principles of Physics demonstrate.

Mirror.jpg picture by xtaintedwatersx

If you were behind the focal point of the mirror, your image would be real and inverted.  If you were behind the center of curvature (which is a distance of 2f away from the mirror with f being the focal length), then your image would be smaller, rendering the “magnifying mirror” useless.

So I guess that contact lens wearers like me and makeup fanatics should appreciate this application of physics that we call the magnifying mirror.  However, if you’re as sleepy as I am in the morning, even a gigantic image won’t stop you from inserting a contact lens into the wrong eye.  Or even worse, inserting both into the same eye.  Hmm…am I the only one who has done this more than once?

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