What is the advantage of using an electron microscope compared to an optical microscope?
An ordinary optical microscope uses the visible radiation of wavelength 6000
. but if we use an electron microscope, the electron acts as a wave and it corresponding wavelength is small.
As we already know the wavelength of an electron is
by suitably arranging 'V' (say 300 volts) the wavelength of the electron can be made to
As the resolving power of a microscope is inversely proportional to the wavelength of light, the smaller the wavelength, the larger the resolving power. Hence, the resolving power of an electron microscope is much more than an optical microscope.
Accelerating the electron through a high potential difference will still reduce the wavelength.
Construction
The electron beam emitted by a filament is accelerated through a large potential difference in an electron gun. The electron beam is subjected to a magnetic field created by an electromagnet.
This beam falls on the object. This beam passes through the object and enters again a magnetic field produced by an electromagnet, which diverges the rays to produce a magnified image of the object. The focusing can be done by adjusting the current in the coil of the electromagnet. The magnification of an electromagnet can be as high as 1,00,000. But it is most used only for scientific research as focusing of the beam is not as easy in the case of an optical microscope.