What is Resolution?

Magnification is how much an image is enlarged under a microscope.

Resolution is the amount of detail you can see in an image. You can enlarge a photograph indefinitely using more powerful lenses, but the image will blur together and be unreadable. Therefore, increasing the magnification will not improve the resolution. This is also known as the resolving power.

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Compound Microscope Resolution:

In a compound microscope, the wavelength of the light waves that illuminate the specimen limits the resolution. The wavelength of visible light ranges from about 400 to 700 nanometers. The best compound microscopes cannot resolve parts of a specimen that are closer together than about 200 nanometers.

1 nanometer = 0.001 microns = 0.000001 millimeter = 0.00000004 inch

Dissection Microscope Resolution:

Just like in a compound microscope, the wavelength of light limits resolution. This microscope does not use light to see through the specimen, but uses light to aid in viewing the specimen under magnification. The resolution of the dissecting or stereoscope is about 120 nanometers.

Confocal Microscope:

Like the compound light, the resolution for a confocal microscope is about 1.2 nanometers.

Scanning Electron Microscope Resolution:

In a SEM, an electron beam scans rapidly over the surface of the sample specimen and yields an image of the topography of the surface. The resolution of a SEM is about 10 nanometers (nm). The resolution is limited by the width of the exciting electron beam and the interaction volume of electrons in a solid.

The resolution of a TEM is 1,000 times greater than a compound microscope and about 500,000 times greater than the human eye.

Transmission Electron Microscope Resolution:

In a TEM, a monochromatic beam of electrons is accelerated through a potential of 40 to 100 kilovolts (kV) and passed through a strong magnetic field that acts as a lens. The resolution of a TEM is about 0.2 nanometers (nm). This is the typical separation between two atoms in a solid.