Diffraction at Your Finger Tips Readers may be interested in the following diffraction demonstration which requires no set-up at all, yet is clear and accessible. Focus your eyes on a distant bright light, then interpose your thumb and forefinger at about reading distance from your eyes. As you slowly bring the tips of the fingers together a series of dark and bright interference lines, parallel to your finger-tips, will sppear. These arise from diffraction a t the finger edges. I ask students to follow this procedure in class when I first talk about diffraction; it is never-failing, and generates a buzz of real interest.
L. Glasser University of Me Witwatersrand Johannesburg, 2050 S O W Africa
Volume 65
Number 8
August 1986
707
