A date with physicist

Jay Waller decided on a quiet, dimly lit Italian restaurant, complete with old wine bottles and romantic candles. After a bottle of white wine arrived, he poured his date a glass and then called her attention to the play of bright lines and spots that danced on the tablecloth as chance disturbance (actually his knee) gently shook the table. He casually explained how people have spent a long time trying to understand such plays of light, called caustics, which are due to how the surfaces of the wine and the wine glass fold the rays of candle light onto themselves, focusing the rays to form especially bright places. The pattern on the tablecloth is actually a two-dimensional slice through a three-dimensional pattern. To show this, Jay moved his hand through the pattern from the tablecloth to the wineglass, to show her how the lines changed in midair. Surely, he thought, this would produce a second date with her. 

But then disaster hit. As they waited for the appetizers, he told her just how wonderful her eyes were, being so blue. He quickly explained the blue was due to the scatter of blue light out of the white light illuminating the iris. Tiny particles (including proteins and fats) in the iris scatter more blue light back outward than the other colors. If the back of the iris is generally black, then the blue light can be striking, as in her gorgeous eyes. Only then did she inform him that her eyes were, in fact, green. And as he glanced at them, he knew from her piercing look (a green that almost glowed in the dark) that there would be no second date with her.