A compound microscope is a scientific optical instrument vital for examining microscopic objects. The scope allows you to see minute objects in tremendous detail that would otherwise be impossible with the naked eye. For example, suppose you need to examine blood samples, bacteria, plant cell structures, chromosomes, pond water, or other objects at a cellular level. In that case, a compound scope is the only way to do this.
Most people recognize a compound microscope when they see one. Usually, these are the devices lab technicians use in school labs or on crime programs on television. The user looks through two eyepieces to examine a specimen on a slide (a piece of glass). So, buying a compound microscope is usually relatively inexpensive and is ideal if you have a hobby of studying microorganisms.
This article is a complete guide to the compound microscope. You will learn about the various types of compound scopes, what they are used for, and the advantages of using this type of magnification device.
What Is a Compound Microscope and How Does It Work?
A compound microscope is an optical instrument that uses a compound lens system to produce a two-dimensional magnified image of a specimen. Also called a biological microscope, it usually has two ocular lenses and several microscope objectives to create high magnification. Compound microscopes are typically for examining slide specimens and various tissue samples.
A compound microscope works using a visible light source underneath the specimen. A series of ocular lenses, powerful objectives, and dual eye pieces allows the user to study microscopic items. This works by light permeating the sample, and the lenses bend the light waves to form a cone. By the time light reaches the eyepiece, it is hundreds of times larger than its original size.
Why Is It Called a Compound Microscope?
The term compound microscope comes from the two or more sets of lenses in the scope. The objective lens provides the primary magnification — the part directly above the microscope’s glass slide. The image is then compounded by the eyepiece — the ocular lens or the part of the microscope the user looks through.
Parts Of a Compound Microscope
The compound microscope uses light and glass lenses to magnify the image of a small, thin specimen. As with any optical instrument, several major parts work together to create the real image you see. The main components are the eyepiece, light source, and revolving objectives.
Let’s look in more detail at the parts that make up a compound microscope. The general structure and function of each element are described below.
- Eyepiece: Also called the ocular lens, this is the part you look through. It also works to magnify the image created by the objective lenses. This usually provides magnification of between 5x and 30x.
- Nosepiece: The revolving nosepiece holds at least three objective lenses, each with varied magnification power. Turning the nosepiece rotates between the objectives.
- Objective lenses: A compound microscope has between three and five optical lens objectives. These usually have a magnifying power of between 4x and 100x. The total magnification power is the combined totals of the ocular lens and objective lens.
- Stage: A flat platform that holds the slide or specimen. A mechanical stage can be added for precise control of slide position when viewing tiny specimens or making measurements.
- Diaphragm or iris: This part of the compound microscope can adjust the amount of light passing through your specimen, allowing you to control brightness and contrast for optimum viewing conditions.
- Illumination system: The illumination system includes a light source, typically an electric bulb, and a mirror or other light-directing mechanism for focusing light into the bottom of the microscope body tube. This is why it is sometimes called a compound light microscope.
- Adjustment knob: This microscope part adjusts the level of detail when examining a specimen.
- Arm: The main part of the upright scope connects the nosepiece to the base and supports all the microscope components above it.
Compound microscopes can be divided into other types of microscopes depending on the intended purpose. For example, a phase-contrast microscope, polarizing microscope, metallurgical microscope, biological microscope, and fluorescence microscope are also types of compound microscopes.
Compound Microscope Lenses
As with any type of microscope, the quality and type of lenses are the most critical components. The two types of lenses in a compound microscope are objective lenses and ocular lenses.
Ocular Lens
The ocular lens is the eyepiece of a microscope where you view and analyze the magnified image of the specimen. This type of lens increases magnification between 5x and 30x; however, 10x eyepiece magnification is standard. Typically, compound scopes have a binocular eyepiece, which is the easiest to use. However, scopes can have monocular or trinocular eyepieces.
Objective Lens
A compound microscope has three to five objective lenses on a rotating nosepiece. Each lens has a set magnification power, and they can increase magnification between 4x and 100x, depending on the type of scope.
A word of warning: Avoid any type of compound scope promising magnification levels of 2000x. These scopes provide false magnification and have poor resolution.
What are the Characteristics of a Compound Microscope?
The essential characteristic of a compound microscope is its magnification. The eyepiece compounds the image produced by the objective lens to allow you to see detailed images of microscopic cells or specimens in high resolution.
For example, let’s say that the ocular lens has a standard magnification power of 10x. Then if the objective lens is 40x, the total magnification would be 400x — enough to see tissue and samples at a cellular level.
Another essential characteristic of a compound microscope is its depth of field. The depth of field refers to the distance that an object can be moved away from or toward the microscope without losing focus. The depth of field in microscopy is vital because it affects how much you have to move the specimen slide to see specific portions of a specimen.
What are the Advantages of a Compound Microscope?
Compound microscopes have various useful features and functions and have advantages over simple microscopes or electron microscopes. Some of its benefits include excellent magnification power, relatively low cost, its own light source, and ease of use. Let’s look at these in more detail.
Compound Microscope Magnification Power
A compound microscope achieves excellent magnification and is relatively easy to use. The combination of ocular lens and objective lens results in superb magnification. Even the most basic compound scope can magnify specimens up to 1000x — enough for school labs or hobbyists.
Microscope for a Reasonable Price
Compound microscopes are relatively cheap to buy. For example, a basic model with three objectives could cost as little as $100. However, for a reasonably-priced standard compound microscope to do serious study, expect to spend a few hundred dollars on a quality binocular compound microscope.
Light Source on the Microscope
Modern microscopes have a halogen or LED illumination source. This allows you to analyze liquids, blood cells, tissue, bacteria, skin cells, and other microorganisms. This is different from a stereo microscope that only is used for samples where light can’t pass through.
Compound Microscopes are Easy to Use
The best thing about buying a compound microscope is that it’s easy to use. The upright scope is small and compact, and easy to store. In addition, because it uses multiple lenses, compound microscopes can reveal a tremendous amount of detail for such a small unit.
What is a Compound Microscope Used For?
A compound microscope has a wide range of applications where it is vital to study cells or liquids at a microscopic, cellular level. The scope contains a complex magnification system that increases magnification dramatically. Here are some of the ways you can use a compound microscope:
- Examine cells and tissues to check for contamination or bacteria
- Carry out forensic examinations of samples taken from a crime scene
- Identify diseases in tissue samples
- Use in school and college when conducting academic experiments
- Look for organic pollutants in soil samples, pond water, or drinking water
- Studying the microbial world of viruses and bacterial that would be impossible without powerful magnification
- Research plant cells and other microscopic living microorganisms
Compound Microscope — In Conclusion
A compound microscope is an essential piece of equipment used in the fields of biology, science, medicine, and forensics. The high-power microscope is also excellent for hobbyists who want to look at specimens in great detail. Compound microscopes are also very affordable and easy to use.
When looking for a quality compound microscope, choose one that is within your budget and has the level of magnification you require.