Floor 1 | Mirrors in Mind
Experimental Stations 1 to 6
On a hexagonal table is a circus of hands-on activities, all to do with reflections in every-day life.
E1: What’s in a surface? An object on a glass mirror actually ‘floats’ 1-2mm above its reflection. On a polished steel surface, it sits without floating, but the metal is easily scratched. The bronze plate is rather soft: the earliest Chinese and Greek mirrors were thin polished discs made of bronze.
E2: Reflections off curved surfaces: Examine the ways the bright letter ‘F’ is reflected off curved glass when the reflecting surface is hemispheric, cylindrical, concave and convex.
E3: Everyday curved mirrors: The car wing-mirror always shows an undistorted image, but its distance can be very deceptive. A shaving mirror shows up every facial blemish – just what you need but rarely want to see first thing in the morning! Look at yourself in the bowl of a spoon. What happens to your reflection on its convex back? Use the half cylinder and point-light to create a caustic curve: have you ever seen this in a teacup?
E4: Polarisation: Polaroid sunglasses block horizontally-vibrating light. Two Poraloids, crossed, let through almost no light. Check the glare off glass and metal: from which is reflected light polarised?
E5: Interference: The butterfly’s wing has a surface structure as fine as a diffraction grating. Depending on the angle of illumination, it is jewel bright (light reinforcing light – constructive interference) or dull aquamarine (light cancelling light – destructive interference). Interference patterns on banknotes and credit cards are so hard to reproduce it makes money and cards very hard to counterfeit.
E6: Unwanted reflections: To prevent stray reflections off art-gallery masterpieces, anti-reflection glass can be used. One problem: shininess is lost too. By etching a reflective surface systematically, dull and shiny areas can be combined to decorative effect – think gift wrapping!
