Can Sunlit Leaves With Liquid Drops On Their Surface Be Burnt
Tamás Stonawski · 2013
My students learn elementary optics in their 11th school year, including the use of light rays in understanding the effect of focusing. In a problem of one of their physics books the task is to search for the causes why leaves can be burnt in hot summer after being watered. As a solution, the book indicates the convex-lens-like behaviour of water drops focusing sunlight on the leaf surface and thus burning them this way. After reading some publications [1-4] of Gabor Horvath and his colleagues on this topic, listening to his lecture and watching a short film about this subject broadcast by the Hungarian Television [5], I recognised how exciting this issue could be for secondary grammar school students, who could make an experiment with sunlit plant leaves covered by liquid drops. I had a few more ideas with which the problem could be approached and examined from a different physical point of view [6].