Microscopy
Microscopy and Cell Observation
Overview of Microscopy
- Microscopy is the science of using a microscope to view objects that are too small to be seen with the naked eye.
- The first microscope was invented in the late 16th century by Zacharias Jansen.
- Modern microscopes can magnify objects up to 1,000 times their original size, which allows us to study cell structures in detail.
Types of Microscopes
- The light microscope uses light to illuminate the specimen. It can magnify up to 1,500 times.
- The electron microscope uses a beam of electrons instead of light. It can magnify up to two million times.
- Electron microscopes are much more powerful but also a lot more expensive. They are usually found in professional laboratories.
Microscope Components
- The eyepiece or ocular lens is where you look into the microscope. It usually has a magnification of x10.
- The objective lens collects light from the sample. There are usually several on a rotating disk, each with a different magnification.
- The stage holds the slide. It can be moved up and down to bring the specimen into focus.
- The condenser lens focuses the light on the specimen.
- The light source illuminates the specimen.
- The coarse and fine adjustment knobs modify the focus.
Preparing Slides for Observation
- Stains or dyes are often used to help to see certain parts of cells more clearly.
- Hydrophilic stains, such as iodine or methylene blue, are water-soluble and bind to water-containing tissues.
- Hydrophobic stains, such as Sudan stains, bind to nonaqueous cells components like fat.
- Always take appropriate care when handling stains as they can be toxic and a hazard to the skin and eyes.
Using Microscopes
- When adapting to a new magnification, use the coarse adjustment knob first to bring the sample into view.
- Then use the fine adjustment knob to get a clear view.
- Always start at the lowest magnification and work up to higher powers.
- Remember to adjust the light intensity and contrast when the magnification is changed.
- Store microscopes properly to avoid damage and dust accumulation. Always cover the microscope when not in use.
Electron Microscope vs. Light Microscope
- Electron microscopes allow us to view objects far smaller than those viewable with a light microscope, such as viruses and the ultrastructure of cells.
- They provide high resolution images due to short wavelength of electrons.
- However, they're very expensive to buy and use, demand high voltage, and samples have to be treated before they can be viewed.
- In contrast, light microscopes are far more readily available and easy to use, and are suitable for viewing live organisms.
- They are less powerful, but they can be used in a normal laboratory or classroom, and can be used to observe phenomena such as cell division in real-time.