On Mon, 19 Sep 2005 15:07:58 +0100, Janet Baraclough
wrote:

The message
from Pam Moore contains these words:

On Sun, 18 Sep 2005 20:30:37 +0100, Jaques d'Alltrades
wrote:


Sun can't burn the leaf through drops of water - 's against the laws of
physics.

But it can and does! That's why you shouldn't water in bright
sunshine, though sometimes the sun comes out too soon after rain and
the same thing happens.

So how is it, that all leaves and plants growing in the open, are not
a mass of burns from sun on raindrops? Why is it that the paintwork of
houses, and cars, is not pitted with a zillion burns from sunrays
through raindrops? Why is it quite safe to walk in rain followed by sun,
without risk of the painful little skin burns friends happily inflicted
on each other with a lens in science classes?

Have you never burned a piece of paper by focusing the sunlight with a
lens?

Yes, but sunlight on a raindrop falls on a reflective convex surface.
Lenses to ignite paper had to be held the opposite way, and at a
distance from the paper, to fucus the beam, otherwise they didn't work.


So, Janet and Rusty, are you telling me it's Ok to turn the hose on my
plants in full sun, when I have many times heard the advice not to?
Janet, which would you prefer to start a fire, leaves or metal?
Also, in my experience lenses are convex too.
Remember how still you had to keep the lens to burn paper? Walking in
the rain is a bit different?

Pam in Bristol