- Seal the small end of an eyedropper in a flame.
After it cools, cut one inch off the end with a file.
- Punch a hole in the centre of a 2 inch square
piece of light card so it fits snugly over the tip of the eye dropper.
- Remove the cardboard and make cuts shown by
the solid lines.
- Bend the card down along the dotted lines to
- Blacken the side of each vane by holding the
card carefully over a candle.Mark one side with an "X"
- Stick the large end of a needle into a cork
and place the cork in the glass jar.
- Set the eyedropper tip and cardboard vanes
over the needle.
- Fasten the lid and try to remove as much air
as possible witha vacuum pump.
Since most of the air has been removed from inside the
radiometer, the paddle wheel or vanes are free to move. Normally the
vanes would strike air molecules and be slowed or stopped. With the air
removed, the slightest sunlight energy striking the vanes will start
the paddle truning.