What a marvel of science it is to be able to look into a mirror and see a reflection of oneself! Did you ever wonder how this happens?
It’s not just humans who like to preen in front of a looking glass; dolphins and apes also are drawn to the image of themselves. When you look into a mirror, conservation of energy is working its magic on light. When rays of light travel and hit an object, it has to go somewhere, so it reflects from you into the silver coating behind the glass in the mirror, and then bounces back again.
There are actually three types of mirrors: a plane mirror that shows you a reasonable approximation of the image but it is shifted from left to right; a converging mirror where light rays appear to come from in front of the mirror and appear bigger than they really are; and a diverging mirror where objects appear smaller and further away than they actually are.
While most mirrors are made of sheets of glass, the back of which has been coated with reflective silver material, there are other examples where the same principal of reflected light can be found. Do you see yourself in a glass window as you walk by? In a calm surface of a lake? A polished spoon? The effect of double reflection of light is still applying, but the mirror will supply the best image as it’s been constructed for the sole purpose of giving you an accurate reflection.
Ever wonder how the suspect in an interrogation room in your favourite television crime drama can be seen but not see out of the window? It’s actually a one-way mirror with a reflective coating applied in a very sparse thin layer, only about half of what it needs to make a real mirror. The room in which the glass looks like a mirror is kept very brightly lit so the light reflects back from the mirror’s surface. The glass on the other side is in a room that’s deliberately kept much darker. The suspect sees only his own reflection, while the detectives on the other side can see everything that’s going on in the interrogation room. If the lighting is reversed in either room, the one-way mirror becomes a window and the people in both rooms can see each other.
Think of the mirror's value when used as a rearview mirror in our vehicles! Driving would be a much more challenging activity without their assistance in seeing other vehicles.
Remember the kaleidoscopes we all enjoyed as children? Thanks to mirrors, we were able to view beautiful ever-changing patterns of colours and shapes. It is really constructed with a tube of mirrors containing loose coloured beads and pebbles. When you look into one end and turn the other end to the light, and when you rotate the tube, you are treated to a colourful symmetrical display by mirrors which are set at 45, 60 and 90 degree angles.
So whether it’s looking at a full-length image of ourselves in the bedroom, or amusing ourselves with a kaleidoscope, we have mirrors to thank for a lot in our daily lives!
