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Dear All, Dec 31, 2014
In early Dec., while writing Christmas cards at about 9:30 am, the sun
being at a low angle, I noticed an interesting optical effect.
On the card and on a nearby sheet of white cardboard, both horizontal on
a table, there were sharp parallel shadows of the vertical wires of a SE
facing window screen but no corresponding shadows of the horizontal wires.
But when the cardboard was held vertical, and at slight angle to the screen,
there were sharp shadows of the horizontal wires but no shadows of the
vertical. And when the cardboard was held normal to the sun and near the
screen there were sharp shadows of both horizontal and vertical wires.
Yt, Dave Webster, Kentville
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