Learn about the differences between electron microscopy and light microscopy in one article.
Nowadays, there are not only optical microscopes that can magnify thousands of times, but also electron microscopes that can magnify hundreds of thousands of times, allowing us to have a deeper understanding of the laws of life activities of living organisms. The vast majority of the experiments specified in the biology syllabus of general secondary schools are done using microscopes, so the performance of the microscope is the key to observing good experiments.
Microscope is a precision optical instrument with a history of more than 300 years. Since the introduction of the microscope, people have seen many previously invisible tiny organisms, but also the basic unit of biology: the cell.
What is a light microscope:
A light microscope is an optical instrument that uses optical principles to magnify and image tiny objects that are indistinguishable to the human eye, thus allowing people to extract information about microscopic structures.
What is an electron microscope:
An electron microscope is a large-scale instrument that uses an electron beam as an illumination light source, and images on a fluorescent screen through the transmission or reflection of the electron stream on the sample and the multi-stage magnification by electromagnetic lenses. While optical microscope is an optical instrument that uses visible light illumination to form a magnified image of a tiny object.
1. Different imaging principles
In the electron microscope, the role of the electron beam on the sample being examined by the electromagnetic lens amplification, and then hit the screen imaging or role in the photographic film imaging. The mechanism for the difference in electron intensity is that when the electron beam acts on the sample to be examined, the incident electrons are scattered by collision with the atoms of the substance. And the object image of the sample in the optical microscope is presented by the brightness difference, which is caused by the difference of light absorbed by different structures of the sample to be tested.
2. Samples used are prepared in different ways
The process of preparing tissue and cell specimens for electron microscopic observation is complex, technically difficult and expensive. Special reagents and manipulations are required in the steps of material extraction, fixation, dehydration and embedding. Finally, tissue blocks need to be placed in an ultrathin slicer and cut into ultrathin specimens with a thickness of 50-100 nm. Specimens observed under the light microscope are usually placed on slides, such as common tissue section specimens, cell smear specimens, tissue press specimens and cell drop specimens.
3. Different light sources
The illumination source used in an electron microscope is the electron stream emitted by the electron gun. The source of illumination in a light microscope is visible light (sunlight or light). Since the wavelength of the electron stream is shorter than that of light waves, the magnification and resolution of an electron microscope is significantly higher than that of an optical microscope.
4. Different lenses
The objective lens that acts as a magnifier in an electron microscope is an electromagnetic lens. (Circular electromagnetic coil that can generate a magnetic field in the centre part), the objective lens of an optical microscope is an optical lens made of glass. There are three sets of electromagnetic lenses in an electron microscope, which are equivalent to the condenser, objective and eyepiece in a mirror.
