In the summer when the sun is higher in sky, we get light patterns on our garden fence.

When I first noticed them, they were a bit of a mystery so I went through the back rooms with a large piece of card trying to shadow out the source of the reflection.

I couldn't find one at first because I had assumed the light was bouncing off a mirror or something inside the house.

It turned out to be light bouncing off the double glazing. It seems, at the correct angle of the sun to the window, some light is reflected off the first pane of glass while some gets through and reflects off the second.

I don''t know if all the light comes straight out or if some is reflected back on to the second pane before it is again reflected outwards. My suspicion is there may be a number of reflections, which could account for the bright and dark areas of the resulting pattern.

-Nick Gregory, Woodpecker Crescent, Burgess Hill