Date of issue: June 17, 1988
Printer: Ashton-Potter Limited
Series: Canada Day 鈥� Science, Technology, Canadian Innovations in Energy, Food, Research and Medicine
Design: Roger Hill
Electron Microscope
Microscopes initially used a candle or the sun to illuminate the object to be viewed 鈥� hence the designation 鈥渓ight鈥� microscope. Early ones were limited by low resolution, which is largely determined by the wavelength of light. Improvements in lens manufacture and microscope design led to the achievement of the light microscope鈥檚 maximal resolution 鈥� about 200 nm 鈥� in the early 20th century. An electron microscope uses an electron as the 鈥渋lluminating鈥� source. Since its wavelength is much less than that of light, its resolving power is more than 1000 times that of the light microscope.
The first electron microscope was developed in Germany in the early 1930s. The first North American version was constructed in 1938 by James Hillier and Albert Prebus, graduate students under the supervision of Professor E.F. Burton at the University of Toronto. The device was initially developed as an instrument for physicists. However, its potential applications in medical research and diagnosis were soon realized and were followed by numerous scientific investigations in the mid 20th century.
The Stamp
The stamp shows Hillier and Prebus鈥檚 invention on top of a diagrammatic representation of part of its structure. A number of bacteria as seen by the microscope are evident in the circle above.
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