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Q & A: Why is your reflection upside down in a spoon?

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Q:
What is physics, and what does physics have to do with your reflection being upside down in a spoon?
- Jessica (age 13)
Camptonville
A:
Jessica -

Let me take your questions one at a time. We’ve actually already answered your first question, "What is physics?".

But your second question hasn’t been answered yet, so I’ll do that now. When you look at yourself in a mirror (and a spoon is basically a curved mirror), what you see is the image that’s produced when light bounces off of your face, off of the mirror, and comes back to you. If you’re looking into a flat mirror, the light will come straight back to you without bending at all. But a curved mirror will bend the light differently.

When the light bounces off of your face and then off of a curved mirror, it won’t come straight back at you, but will go off at an angle, instead. You can imagine this as if one little part of the mirror (or the spoon) was flat, then the light wouldn’t bounce straight back ... like if you bounced a ball off of the ground, but you did it at an angle - it wouldn’t come straight back at you, but it would go off at the same angle as it hit the ground.

Here’s a really good animation of what I’m talking about:

Candle

(This is taken from the Shockwave Physics Studios website.)

This is sort of hard to explain, so it may be easier to look at the picture. Basically, the light waves hit the different parts of the spoon at different angles, so they’re all bent a little bit differently. By the time they come back to you, they’ve all bent differently in such a way that they end up making you look upside down.

Hope this explanation helps!

-Tamara

(republished on 07/29/06)

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