The main Difference Between Optical Microscope & Electron Microscope is that an optical microscope uses a light beam to illuminate an object. Under consideration, an electron microscope uses an electron beam to illuminate an object.
Both light microscopes (light microscopes) and electron microscopes are used to see very small objects.
What is an optical microscope?
Optical microscopes use visible light to illuminate those specimens and utilize lenses to produce magnified images. There are two types of optical microscopes. Single lens and compound . Single-lens microscopes use a single lens to magnify an object, while compound lenses use two lenses.
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A real, inverted, and magnified image of the objective lens sample is created inside the microscope, and then the eyepiece , ie, the image formed by the objective lens, is further magnified.
Image of moss leaves ( Rhizomnium punctatum ) under a light microscope ( 400x) . Compare the size of these chloroplasts (green masses) with the more detailed version (from another specimen) taken with the electron microscope below.
What is an electron microscope?
The electron microscope uses an electron beam to illuminate those specimens. A magnetic field is used to bend a beam of electrons, just as an optical lens is used to bend a light beam in a light microscope. Two types of electron microscopes are widely used.
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Transmission electron microscope (TEM) and scanning electron microscope (SEM) . In a transmission electron microscope, an electron beam passes through. A through- specimen objective lens “lens” (actually a magnet) is initially used to produce an image, and a projected “lens” can be used to produce a magnified image on a fluorescent screen.
In a scanning electron microscope, an electron beam is applied to a sample, which emits secondary electrons from the surface of the sample. Anodes can be used to collect these surface electrons and “map” the surface.
Generally, the resolution of SEM images is not as high as that of TEM. However, SEM does not require electrons to pass through the sample, so it can be used to investigate thicker samples. In addition, the images generated by the SEM reveal more detailed details of the surface.
TEM image of chloroplast (x12000)
SEM images of pollen from various plants (x500). Pay attention to the details of the depth.
Resolves the ability to distinguish between two different points in an image . The higher the resolution, the sharper and more detailed the image. Since light waves are diffracted, the ability to distinguish between two points on an object is closely related to the wavelength of light used to see the object.
This is Rayleigh standard . Waves also cannot reveal details at spatial intervals smaller than their wavelength. This means that the shorter the wavelength used to see the object, the sharper the image.
The electron microscope utilizes the wave nature of electrons. The wavelength for electrons accelerated to the typical voltage used in the Dobroy wavelength TEM (ie, the wavelength associated with the electron) is about 0.01 nm, whereas visible light has a wavelength between 400 and 700 nm. Have.
And obviously, electron beams can reveal far more detail than visible light. In reality, the resolution of the TEM tends to be about 0.1 nm instead of 0.01 nm due to the influence of the magnetic field, but the resolution is still about 100 times better than the resolution of the optical microscope. The resolution of SEM is rather low, about 10 nm.
Difference between optical microscope and electron microscope
A beam of visible light (wavelength 400-700 nm) is used to illuminate the light microscope sample.
An electron beam (wavelength ~ 0.01 nm) is used to illuminate the electron microscope specimen.
Optical microscope A light beam is bent using an optical lens to magnify the image.
Use an electron microscope magnet to bend the electron beam and magnify the image.
Optical microscope It has a lower resolution, about 200 nm, compared to an electron microscope.
The electron microscope can have a resolution of about 0.1 nm.
The optical microscope has a magnification of about 1000 times.
The electron microscope has a magnification of up to about 500,000 times (SEM).
An optical microscope does not necessarily require a power source to operate.
Electron microscope Electricity is needed to accelerate electrons. Also, unlike a light microscope, the sample must be placed in a vacuum (otherwise electrons can scatter from air molecules).
Optical microscope It is much cheaper than an electron microscope.
Electron microscope is relatively expensive.
The optical microscope is small and can be used on the desktop.
The electron microscope is quite large and can be as tall as a human.
Young, HD, & Freedman, RA (2012). University of Sears and Zemansky Physics: With Modern Physics. Addison-Wesley
“Punktiertes Wurzelsternmoos ( Rhizomnium punctatum ), Laminazellen, 400x vergrößert” Christian Peters-Fabelle Flow (photographed by Christian Peters)