Introducing mirror symmetry

I thought I would introduce the idea of mirror/reflective symmetry to the small boy and see if he found it interesting. Mirror symmetry means that something is the same on both sides of a central dividing line, and an easy way to show this is using a mirror.

We've previously played with mirrors when we made a kaleidoscope (which worked well but he didn't seem very interested in; we will have another go when he's a little older), but we've not talked about symmetry at all. However, he had a clearer idea than I anticipated about patterns when we played with some Duplo brick patterns recently so I wasn't quite sure what he might already have realised about symmetry.

I decided to start with some letters as he's quite into learning to read at the moment, and many capital/upper case letters are symmetrical. I printed some big letters with half of them missing (I just put a white box over it in PowerPoint) and drew a dashed line where the mirror needed to be placed. 

He wasn't at all interested when I gave him the (shatterproof) mirror and the half letters, but a few minutes later I showed him how he could make the whole letter appear and suddenly he was keen to try more letters.  The letters A, B, C, D, E, K, M, T, U, V, W and Y (in many fonts) have a single line of mirror symmetry. I only printed out a few of these, but he did them all a few times, placing the mirror on the line and announcing which letter he could see. I introduced the phrase 'mirror symmetry' whilst we were talking about what he could see.

H, I, and X have two lines of symmetry.  I printed H twice with different halves (top/right) missing so he could see this for himself. By the time we got to this one, he was able to guess that the letter he would see both times would be H.  I also did X the same way, and he enjoyed that one more as 'X' is one of his favourite Alphablocks in the CBeebies programme.

I had printed out some complete symmetrical letters so he could experiment with where he needed to place the mirror to see a complete letter. These were alongside some letters that weren't symmetrical, so he puzzled for a while before telling me they didn't work. He also had fun with the letter P which he found wasn't symmetrical, but if he put the mirror across it horizontally, it either looked like B on one side or I on the other.

Some of the letters and an example of how we used a mirror

We didn't spend a long time on this before his brother tried to eat the paper and take the mirror and we gave up (and nor did I take any photos at the time as I was too busy helping one small boy and distracting the other!), but we will have another go with something that explores mirror symmetry again soon.