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Practices of Science: Microscope Use

NGSS Science and Engineering Practices:

NGSS Crosscutting Concepts:

Microscopes are useful tools for visualizing small structures in great detail. There are two common types of microscopes used in laboratories when studying algae: the compound light microscope (commonly known as a light microscope) and the stereo microscope (commonly known as a dissecting microscope).

 

A light microscope is used to visualize objects flattened onto glass slides in great detail. It typically has a magnification power of up to 1000x. A light microscope might be used when examining individual cells within living tissue.

 

A dissecting microscope is used to view three-dimensional objects and larger specimens, with a maximum magnification of 100x. This type of microscope might be used to study external features on an object or to examine structures not easily mounted onto flat slides.

 

<p><strong>SF Fig. 2.2.</strong> (<strong>A</strong>) Light microscope</p><br />
<p><strong>SF Fig. 2.2.</strong>&nbsp;(<strong>B</strong>) Dissecting microscope</p><br />


<p><strong>SF Fig. 2.2.</strong> (<strong>C</strong>) Filaments of the freshwater green alga <em>Spirogyra</em> sp. viewed under a light microscope with 300x magnification</p><br />
<p><strong>SF Fig. 2.2.</strong>&nbsp;(<strong>D</strong>) Red macroalga <em>Asparagopsis taxiformis</em> viewed under a dissecting microscope</p><br />


 

Both microscopes have similar features. Each microscope has an eyepiece as well as a light source. Light microscopes usually have eyepieces that are magnified 10x plus multiple objective lenses that are magnified between 4x and 100x (SF Fig. 2.2 A). The total magnification is calculated by multiplying the eyepiece magnification (10x) by the objective lens magnification (e.g., 40x), for a total magnification would be 400x. On a light microscope, a sample is placed on a glass slide and light is passed through the sample from underneath the stage. This type of microscope shows great detail of small, thin objects. To view thicker objects, the tissue sample must be thinly sliced and prepared on a glass slide in two-dimensions. With a dissecting microscope whole objects can be viewed in three dimensions. Samples do not need to be sliced, and larger, live animals can be observed. Light can be passed through from underneath the sample, but also from the top or side using an external light source. However, the magnification power of the dissecting microscope is less powerful than that of a light microscope.

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.