It is often stated that plane mirrors invert left to right but not top to bottom.

It is given as the reason why the word AMBULANCE is often written on the front in 'mirror writing'.

Yet if you are followed by that same ambulance and it indicated to turn right or left you do not see the indicators switched.

So if the ambulance indicated left behind you you see the left hand indicator flash in your mirror.

If anyone has a clear predictive explanation of images in plane mirrors I would be grateful for them to post it.

Edited December 16Dec 16 by studiot

40 minutes ago, studiot said:

It is often stated that plane mirrors invert left to right but not top to bottom.

Incorrectly stated. See below.

40 minutes ago, studiot said:

It is given as the reason why the word AMBULANCE is often written on the front in 'mirror writing'.

Yet if you are followed by that same ambulance and it indicated to turn right or left you do not see the indicators switched.

So if the ambulance indicated left behind you you see the left hand indicator flash in your mirror.

If anyone has a clear predictive explanation of images in plane mirrors I would be grateful for them to post it.

Mirrors invert front to back.

When you look at the ambulance in the mirror, you are looking forward. To look at the ambulance itself, you must rotate 180 degrees to see it. It’s the rotation that causes the left-right inversion. Not the mirror.

I did a youtube video of this on my blog back in the day but Google is so messed up these days I don’t know if I can find it.

edit

searching the blog itself was much more productive

http://blogs.scienceforums.net/swansont/archives/13984

Also the previous post, in that link

There was also an episode of QI that dealt with this:

One other thing that Sandi Toksvig could have done was flip the card upside down to reinforce that it was indeed she and not the mirror that flipped the writing.

Thanks for that folks.

I'm not sure about theatrical Toksvig, but I appreciate the answers.

I think they are consistent with my understanding that it is about the direction of observation and best explained to someone who has at least the most basic Tech Drawing.

5 hours ago, studiot said:

Thanks for that folks.

I'm not sure about theatrical Toksvig, but I appreciate the answers.

I think they are consistent with my understanding that it is about the direction of observation and best explained to someone who has at least the most basic Tech Drawing.

It's a bit of a grisly picture, but when I look at myself in a mirror, I think I'm essentially seeing the 2D surface of my face from behind with all the wet bits removed (and depth inverted).

This is what comes of four decades of fiddling around with contact lenses.

Edited December 17Dec 17 by sethoflagos