Steve wrote:

I have never believed that this happens, at least not with water. I
don't believe the part of a leaf under a drop of water can possibly get
hotter than the adjacent areas. Sort of an urban legend. Perhaps a
suburban legend, in this case, since I have seen the same reasoning in
reference to watering lawns while the sun is shining. (There may be
other good reasons to avoid watering lawns while the sun is shining, but
I don't believe in the lens theory.)

Steve

You are right. Not necessarily a lens. I think it fools the leaf into
reacting as if it were a cloudy day because it is cooler in one spot.
The light is no less intense, thus the burn. Similar to having your
eyes dilated and not wearing some type of tinted glasses. Low light or
thin leafed plants are more susceptible.

Nancy