Tuesday 15 May 2012


When a ray of light travels from one medium to another the beam is bent, and some of the light is reflected back by the surface. As the angle of the beam changes, more and more light is reflected back until an angle where none of the light makes it thought the surface.

These bits of basic optics tend not to have much effect on people's everyday lives. If you're an angler you probably know that the fish can only see out of the water above them, and that you can hide from them below a sort of shiny horizon. If you drive, then you most likely have a little toggle on the bottom of the rear view mirror which changes its angle. When you flick the toggle you start to use the front face of the glass as the reflecting surface, rather than the mirrored back.

For me, a poor grasp of optics had a much more immediate and humiliating effect. Last week I was walking past a large inner-city housing development when one of my friends told me that I had curry on my face. I took my (large, foppish) handkerchief from my pocket, moistened its corner, pursed my lips and leant towards what I thought was a reflective surface. It turned out that it was in fact a window, and that I was staring into somebody's living room. It contained furniture, decorations, and a young woman behind an ironing board staring back at me in horror and disbelief.

Richard "Total Internal Reflection" B

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