A microscope is a device used to observe minute objects invisible to the naked eye. It is one of the important discoveries that helped progress science and medicine. This microscope is of two types like
The light microscope also called a compound microscope is a regular microscope we observe in labs.
Electron microscope.
Both are meant for the magnification of minute objects, but the latter’s resolution is very high compared to the former.
Difference between a light microscope and an electron microscope
| Properties | Light Microscope | Electron Microscope |
|---|---|---|
| Principle | The visible light passes through the specimen. The magnified image formed by the objective lens is further enlarged by one or more additional lenses (eyepiece). | In an electron microscope, a beam of electrons is used to magnify the specimen images at very high resolution. |
| Resolving Power | The light microscope has a less resolving power of around 0.25µm to 0.3 µm. | The resolving power of an electron microscope is (0.001 µm), which is many folds higher than the light microscope. |
| Discovered by | In 1590 Zacharius Jansen and his father Hans designed the microscope. | In 1931 Ernst Ruska and German engineer Max Knoll, are physicists who invented the electron microscope. |
| Method | The glass lenses and the visible spectrum of light are involved in a light microscope. | In an electron microscope, the electromagnetic lenses and the beam of electrons for image formations are involved. |
| Vacuum | There is no requirement for a vacuum condition to work with a light microscope. | Since an electron microscope uses an electron beam. Its short wavelength can be retarded and deflected easily by the molecules in the air. So, a vacuum condition is mandatory in an electron microscope. |
| Mounting the specimen | In a Light microscope, the specimen is mounted on the glass slide attached to the stage. | In the Electron microscope, the specimen is mounted on the metallic grid placed on the stage. |
| Magnification changes | In the light microscope, the magnification can be adjusted by the use of different objective lenses. | In the electron microscope, the power of the electric current adjustments changes the magnification. |
| Visibility | Once the object is focused, the image in the light microscope can be observed with the naked eye. | Once the object is focused, the image of the object is captured by a fluorescent screen or photographic plates. This helps us to see. The naked human eye cannot observe the image as the electron beam is not visible. |
| Cost factor | The light microscope is inexpensive and hence widely used in schools and college labs. | The electron microscope is very expensive in terms of instrument and usage. |
| Size of instrument | The light microscope is tiny; it occupies a place of a desktop computer. | The electron microscope requires ample space. A separate facility for systems like cooling, vacuum, image processing, etc. is needed. |
| Photographs | The photograph of the image in the light microscope is colored because the staining procedure will produce colors. | In an electron microscope, the photograph is not colored; only black and white images are captured, but if we want a color pseudo-color (false color) is used |
| Specimen size | The specimen size should be less than 5µm thick to be easily visualized. | To visualize the image in the electron microscope, the specimen size should be only 0.1µm. |
| Filaments | In the light microscope, the use of filament is absent. | A tungsten filament is used to produce the electron beam in the electron microscope. |
| Image Formation | The light passes through the specimen and reaches the objective lens. From here it is re-directed and passes through the eyepiece for visualization. | The electrons emitted in the vacuum are attracted by the specimen and appear dark on the micrograph, while other areas appear bright. |
| Resolution | The typical resolution of the light microscope is 200nm. | The typical resolution of the electron microscope is 0.5nm. 0.5nm. |
| Magnification | The magnification range for the light microscope is between x1000 and x2000. | The magnification range for the electron microscope up to X 10, 000,000. SEM: X100, 000. TEM: X250, 000. |
| View of Living cells | In the light microscope, we can observe the living cells and their activity e.g., Bacteria movement in action. | Due to the vacuum inside the electron microscope, we cannot observe the living creatures’ movement as they would be dead. |
| Wavelength of radiation | Visible wavelength of i.e., 400-700nm. | The approximate wavelength for the electron microscope is <1nm. |
| Types | The light microscope is of four different types 1) Bright-field microscope 2) Darkfield microscope 3) Phase-Contrast 4) Fluorescent Microscope | The electron microscope is of two basic types like 1) Transmission Electron Microscope (TEM): 2) Scanning Electron Microscope (SEM): |
| Preparation of specimens | Smear preparation 2) Fixation 3) Mounting 4) Dyes 5) Staining | The same preparations as the fixation and staining. The freeze-etching technique is involved in the preparation of the specimen to visualize the image by the TEM and SEM. |