Concave and Convex

In the last experiment, you saw how a car's curved passenger-side mirror changes the way that a reflection looks. Let's play around with curved mirrors again.


Find a large metal serving spoon whose surface is smooth enough that you can see your reflection. Hold the inside of the spoon toward your face and look at your reflection. What do you see? Surfaces that are curved in this way are called concave (remember this word by thinking of the inside curve as a "cave"). Now turn the spoon around and look at your reflection on the outside (convex) part of the spoon. Does it look different from the concave reflection?


Which side of the spoon looks most like what you saw in the car's passenger mirror reflection? Is that mirror concave or convex? Which side would be better as a magnifying mirror?

Puzzling Mirror Mazes

You can use what you have learned about angles of reflection to solve maze puzzles using mirrors. Figure out how you could use mirrors to see hidden shapes. Look at the simple example below:



Start at the shape, then draw a straight line until you come to a mirror (black line). Then make a square turn, and continue until you find another mirror. Make a square turn again, and keep going until you come to the eye. Remember that you can't see through walls (gray rectangles)!

There are 12 mirror maze puzzles in the file attached below. You can easily just print them out. But be careful - they're trickier than the example above! The second file contains the answers.

Have fun!

Mirror Mazes

Answers to Mirror Mazes

Angle In = Angle Out

Enough about mirror images. Now let's talk about how light actually reflects off a mirror's surface. There's even a scientific law that says "The angle of reflection equals the angle of incidence." Huh? It's simple - this law just means that the light reflects off the surface at the same angle it hit the surface with. Angle in = angle out!

Look at the figure below:

Can you see that, in both cases, the angle between the mirror (gray line) and the arrow on the left is the same as the angle between the mirror and the arrow on the right?

You can prove this law yourself. Get a small mirror and a laser pointer (never look into the laser pointer and never point it at someone else). Have someone stand facing a wall, holding the mirror so that it points at the wall. Turn the pointer on and position it so that it shines on the mirror. The laser light will bounce off the mirror and hit the wall. Can you find it? Now move the pointer so that the light hits the mirror at a different angle. Does the spot on the wall move? You can also try keeping the laser still and moving the mirror. You should see the laser spot move whenever the angle between it and the mirror changes - it doesn't matter whether it's the pointer or the mirror that moves.

Mirror Writing

Have you ever seen an ambulance which had the word "AMBULANCE" written backward on the front of the vehicle? Why would they do that? It's written correctly on the sides and back! The answer is very simple. Because the word is written backwards, it appears normal when a driver looks at it through his or her rear-view mirror! You can try this yourself. Copy what is shown below onto a piece of paper, then hold the paper up to a mirror and read the word:Sometimes people have purposefully used mirror writing to try to disguise what they were writing, almost like a secret code. Leonardo DaVinci, the famous Italian inventor and artist, often wrote in this way. No one really knows why he did this.

Some people find it very easy to write backwards. Are you one of them? Try writing your name in mirror writing, then hold it up to a mirror to check. Don't feel bad if you can't. Only about 4% of the population can do this (that's just 4 out of every 100 people). If you are a good mirror writer, then chances are that at least one of your parents is, too, because this ability seems to be something you inherit, like your hair and eye color!

Even if you can't write backwards easily, you can produce mirror writing in three steps. First, write down what you want to say, then look at it in a mirror. Copy down exactly what you see in the mirror, and you'll have backwards writing!

Try reading the message below to see how good you are at decoding mirror writing!Do you agree?

Mirror Images

We are so used to seeing our reflection in a mirror that we sometimes don't really look at what we see. For example, go to a mirror and hold your right hand with the palm facing the mirror. What do you see? You're probably thinking, "Big deal, it's my right hand!". But is that really what it looks like? Now turn your left hand so that the palm is facing you, and compare that to what you see in the mirror. They are the same! In a mirror image, the left and right sides of the image are flipped, and there's no way to make them look exactly the same. Something doesn't have to be seen in a mirror to be a mirror image - your right and left hands are mirror images of each other. There's no way to line them up without turning one of them around:

Can you think of any other parts of your body that are mirror images? If you can't think of any, look down! What about items of clothing? Are your shoes mirror images? How about socks? Gloves and mittens? Hats and scarves?

Mirror, Mirror on the Wall

We use mirrors almost every day to help us comb our hair, to check if there's something gross between our teeth, or just to make funny faces into! But have you ever really thought about how mirrors actually work? This month, we'll explore reflection, solve some mirror mazes, and get instructions on how to build a periscope and a kaleidoscope!