DIFFERENCE BETWEEN LIGHT MICROSCOPES AND ELECTRON MICROSCOPES

same type of microscope, same but different. below will explain some differences between Light microscope and electron microscope:

Understanding of Light Microscope

Light microscopes illuminate their specimens using visible light and utilize lenses to produce magnified images. Light microscopes have two types: single lens and compound.

In a single-lens microscope, a single lens is used to zoom in on objects while a compound lens uses two lenses. By using an objective lens, a real, inverted and enlarged image of the specimen is produced in a microscope and then using a second lens called the eyepiece, the image formed by the objective lens is magnified even further.

Understanding Electron Microscopes

electron microscope
image by:microbenotes.com

Electron microscopes illuminate their specimens using electron beams. Magnetic fields are used to bend electron beams, just as optical lenses are used to bend light beams to light microscopes. Two types of electron microscopes are widely used: transmission electron microscopy (TEM) and scanning electron microscope (SEM). In a transmission electron microscope, a beam of electrons passes through the specimen.

An objective “lens” (which is truly magnetic) is used to first produce an image and using a projection “lens”, an enlarged image can be produced on a fluorescence screen. In scanning electron microscopy, a beam of electrons is fired at the specimen, which causes the secondary electron to be released from the specimen surface. By using anodes, these surface electrons can be collected and their surfaces can be “mapped”.

Usually, SEM image resolution is not as high as that of TEM. However, because electrons are not needed to pass a sample in SEM, electrons can be used to investigate thicker specimens. Furthermore, the images produced by SEM reveal details in greater depth than the surface.

Resolution

resolution microscope

The resolution of an image illustrates the ability to distinguish between two different points in an image. Higher resolution images are sharper and more detailed. Because 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 objects. This is explained in the Rayleigh criteria. Waves also cannot reveal details by spatial separation smaller than the wavelength. This means that the smaller the wavelength used to see the object, the sharper the image.

Electron microscopy utilizes the nature of electron waves. The de Broglie wavelength (ie the wavelength associated with electrons) for electrons is accelerated to the typical voltage used in TEMs around 0.01 nm while visible light has wavelengths between 400-700 nm. Then, the electron beam can reveal more detail than the visible light beam.

The resolution of TEMs tends to be in the order of 0.1 nm rather than 0.01 nm because of the effect of the magnetic field, but the resolution is still about 100 times better than the resolution of the light microscope. The SEM resolution is slightly lower than the order of 10 nm.

Difference Between Light Microscopes And Electron Microscopes

Electron Microscopes
image by bath.ac.uk

Source of Illumination

  • Light Microscopes: The light microscope uses a beam of visible light (wavelength 400-700 nm) to illuminate the specimen.
  • Electron Microscope: Electron microscopes use electron beams (wavelengths of ~ 0.01 nm) to illuminate specimens.

Magnifying Technique

Magnifying Technique

  • Light Microscope: Light microscopes use optical lenses to bend light rays and magnify images.
  • Electron Microscope: Electron microscopes use magnets to bend electron beams and magnify images.

Resolution (Light Microscopes Vs. Electron Microscope)

  • Light Microscope: The light microscope has a lower resolution compared to the electron microscope, around 200 nm.
  • Electron Microscope: Electron microscopes can have a resolution of the order of 0.1 nm.

Enlargement (Light Microscope Vs. Electron Microscope)

  • Light Microscopes: Light microscopes can have magnifications around ~ × 1000.
  • Electron Microscope: Electron microscopes can have magnifications up to ~ × 500000 (SEM).

Operation (Light Microscope Vs. Electron Microscope)

light microscope and electron microscope
Electron microscope || image by:marine.usf.edu
  • Light Microscopes: Light microscopes do not need a power source to operate.
  • Electron Microscope: Electron microscopes need electricity to accelerate electrons. This also requires the sample to be placed in a vacuum (otherwise electrons can spread from the air molecules), unlike a light microscope.

Price (Light Microscope Vs. Electron Microscope)

  • Light Microscopes: Light microscopes are much cheaper compared to electron microscopes.
  • Electron Microscopes: Electron microscopes are relatively more expensive.

Size (Light Microscope Vs. Electron Microscope)

  • Light Microscope: Light microscope is small and can be used on a desktop.
  • Electron Microscope: Electron microscopes are quite large, and can be as tall as a person.

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