This is so cool, I still get a kick out of it. We are so accustomed, and even 'trained' to operate in front of a plane mirror and perform our daily duties - like brushing teeth, combing hair, putting on make-up, reading... - that our brains accept the front/back reversal and we deal with it. However, what happens when you see yourself as others truely do? It's freaky!
Place two plane mirrors vertically at right angles to
each other. Do this simply by taping the back corner while holding one mirror vertically resting against a table edge and the other sitting on the table at the edge. See photo below.
Look into the seam of the mirrors. Adjust the mirrors so you see a single non-duplicated image of your face. This is a "true" image.
Notice anything different? Yep! Our faces are NOT really symmetrical. This is what others see you as. You actually see the right side of your face on your left and your left on your right - unlike a plane mirror. Now, have some fun with it.
Raise you right hand to touch your right ear. It will amaze you at the psychological effect this has. The image actually raises the true right arm, not the mirror image "left" arm we are used to. Explanation? Each side is a reflection of a reflection. The left side is a reflection of the reflection from the right side. Cool, huh? The kids will love this. Another neat effect of this mirror is that you don't have to be in front of it. Place it at eye level and observe as you walk past it. You can ALWAYS see your image. It has about 160o vision area.
Want more fun? Have a student, preferably a girl, apply some make-up while using this true mirror. She simply can't! Heck, I can't even touch my left ear!
3-D Reflection: Place a 3rd plane mirror under the true mirror mentioned above. Throw some chalk dust or smoke around and shine a laser at the 3-D corner so the beam hits all 3 mirrors. Note the beam invariably comes back parallel to itself. Examine this geometrically using the Law of Reflection. I use this as a Lab-based problem on an exam.
ADDENDUM: A while back, I received a nasty email from a company called "True Mirror, Inc" demanding that I stop using the term "True Mirror" since they owned the name! Say, WHAT? I fired back a semi-nasty email reply wondering how they could tell a lowly high school teacher not to use or name a demo that has been around longer than they have been alive. I learned this from my favorite college Prof, Robert Hartford in the early 70's, fer cryin' out loud. Anyway, their reply to my reply was even nastier than mine. They were flabbergasted that I was upset and that I should change my medication... So, with the advise of an attendee at one of my workshops, I changed the name of this page from "True Mirror" to "True Image Mirror". They don't own that one. So, I emailed to tell tham that I had invented a brand-new devise and that they should stop describing their's as a "True Image Mirror". I think they realized the error of their ways after I received a few national awards and my site started getting a few hundred hits a day. They sent me their $200.00 mirror with an apology of sorts stating "...no hard feeling and accept this gift with no strings attached..." Thanks.
Sorta proves my point, eh? Mine costs $0.00. Their's is $200.00. Which do you want to use?