© Reprinted courtesy of Dr. Aikira Tonomura, Hitachi, Ltd., Japan.
An interference pattern builds up on a sensitive detector as electrons pass through two slits, demonstrating both their wave and particle properties. In panel a, eight electrons appear to be randomly scattered on the detector after passing though the slits. As more electrons pass through the slits onto the detector, the pattern appears increasingly less random (panels b and c), until finally a two-slit interference pattern emerges in panel d, which shows the position of 60,000 electrons. The double slit in this experiment was formed in an electron microscope by sending a beam of high energy electrons on either side of a filament with a diameter less than a micrometer. The detector is sensitive enough to detect individual electrons with almost 100% efficiency. (Unit: 5)