Why does an electron microscope have more resolving power than an optical microscope?

Answer 1

Short Answer:

Electron microscopes have much better resolution and are capable of much higher magnification than light microscopes because the wavelength of the electrons is thousands of times smaller than the wavelength of light.

Light microscopes can typically resolve structures to a fraction of a micron compared to electron microscopes which in practice achieve resolutions of a few nanometers. Practically, electron microscope can have almost a thousand times greater resolution than an optical microscope.

The useful magnification of an electron microscope is also in the range of a thousand times greater than an optical microscope.

The actual performance of any microscope depends on its design and lensing system and so significant variation exists in the above practical characteristics and performance of both types of microscopes can be enhanced in various ways.

Long Answer:

An electron microscope uses an electron beam to illuminate a specimen and produce the image.

An optical or light microscope uses a light beam to illuminate a specimen and produce the image.

A microscope of either type is characterized by its magnification and resolving power. The magnification depends on the lensing system and can be increased to any degree, but the maximum useful magnification is limited by the resolving power.

The resolving power of a microscope can not be better than the limits placed on it by the size of the wavelength of the illuminating beam. The smaller the wavelength, the smaller the structures that can be resolved in them image.

Visible wavelengths of light are a few hundred nanometers. An electron microscope operates with electrons accelerated to a few hundred thousand electron volts of energy and with a wavelength in the range of few hundredths of an Angstrom.

An electron microscope has a theoretical resolving power that is much greater than a light microscope and can reveal smaller structures because the electrons used have wavelengths (few hundredths of Angstroms) almost 100,000 times shorter than visible light (few hundred nanometers).

An optimized electron microscope can achieve a practical resolution of a few Angstroms and a useful magnifications in the millions of times.

A good light microscope can resolve structures smaller than a micron but is limited to about a few hundred nanometers resolution. The useful magnification of a light microscope is not much more than a thousand times.

The electron microscope uses electrostatic and electromagnetic fields to act as lenses to control and focus the electron beam and to form an image. An optical or light microscope employs glass lenses.

Answer 2

An electron microscope has a shorter wavelength of electrons compared to visible light in an optical microscope, allowing it to achieve higher resolution. Additionally, electron microscopes use electromagnetic coils to focus the electron beam, which provides better control and precision in imaging compared to optical microscopes that use glass lenses.