Key Concepts: Microscopy

Key Concepts: Microscopy

  • Microscopes are a fundamental piece of equipment in biology. They are used to observe organisms and structures smaller than can be seen with the naked eye.

  • The two main types of microscopes that you will need to know about are light microscopes and electron microscopes.

  • Light microscopes transmit light through a slide containing the specimen, and they can magnify objects up to 2000 times.

  • Electron microscopes use a beam of electrons, rather than light, to produce images with extremely high resolution.

  • Because they use electrons, electron microscopes have a much higher magnification and resolution than light microscopes. They can magnify sample up to 2 million times.

  • Magnification is the extent to which the image of a specimen is larger than the specimen itself. It is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens.

  • Resolution is the ability to clearly see and differentiate two separate points or structures as distinct.

  • Microscopic organisms such as bacteria, viruses and the components of cells (like chromosomes and mitochondria) cannot be seen with the naked eye but can be observed with a microscope.

  • Scientists use stains to make certain parts of a cell more visible under a microscope.

  • Cell theory was developed using the light microscope, which led to the discovery of cells.

  • The invention of the electron microscope allowed scientists to observe and understand the structure of smaller cellular components and viruses.

  • It’s important to understand how to properly use and care for a microscope, including knowing how to adjust the focus, change the lenses for different magnifications, and clean the lenses properly to maintain resolution.

  • When preparing a specimen to view under a microscope, a thin slice (section) is often made so that the light or electrons can penetrate the sample.

  • Always remember: ‘magnification’ is how much larger the image is than the actual size of the object being looked at, whereas ‘resolution’ is the degree of detail you can see in the image.

  • In many cases, a balance must be struck between high magnification and good resolution. Increasing the magnification can sometimes result in a loss of resolution due to limitations in the optics of the microscope.