\sPrince Mohammad University
Introductory Biology
Report
Reem A. Alotaibi
2001100196
Introductory Biology
Section: 201
Dr. Tabassum Ashfaq
Study of Compound Microscope
Aim of the experiment:
Objective of Study:
1- To identify the different parts of the microscope.
2- To know the functions of the different parts of the microscope.
3- To learn the different objective powers of the microscope.
4- To correctly use the microscope to see perfectly clear images of different specimen.
5- To understand the precautions needed while handling a microscope.
Materials Required:
- Microscope.
- Pinus Pollen Grains.
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- Sand.
- Salt.
- Hair.
Parts of a Compound Microscope
The various parts of a compound microscope can be identified with the help of the diagram below:
Figure 1. A typical compound microscope
Parts of a typical Compound Microscope are:
- Base- This part supports the microscope to give physical stability to the instrument.
- Arm- It acts as a handle with the help of which the microscope can be carried from one place to another without causing any damage to the delicate parts.
- Body Tube- This keeps the eyepiece and objective lens at a distance that is appropriate.
- Opening In stage- It allows light to enter in the instrument from the bottom of the instrument.
- Stage- It gives support to the slide under observation.
- Stage Clips- These help to keep the slide in correct position.
- Mirror- It allows the reflection of light for magnification.
- Ocular Lens or Eyepiece- It possesses the replaceable lenses and produces an image for the eye.
- Coarse Adjustment- This part allows the adjustment of the specimen according to the requirement.
- Fine adjustment- It helps in focusing accurately.
- Diaphragm- It helps in regulation of light illuminating the specimen.
- Objectives- These possess lens that is capable of magnification.
- Nose Piece- This part permits the interchange of low and high power objectives.
Working of a Compound Microscope
In light microscopy, the light passes through a specimen and later through a series of magnifying lenses.
A series of finely ground lenses leads to the formation of a clearly focused image that is many times enlarged than the specimen. This magnification may be achieved when the light rays from the illuminator (the light source that is used to illuminate the specimens positioned on the stage) pass through a condenser that has lenses to direct the light rays through the specimen. From here the light rays are passed into the objective lens and the image of the specimen is again magnified by the eyepiece.
The total magnification of a specimen is calculated by multiplying the objective lens magnification by the eyepiece lens magnification. Three different types of objective lenses are commonly used-Low power X 10, High Dry X 40, and oil immersion X 100.
Figure 2. can be referred for better clarity on magnification concept.
Figure 2: Calculation of Total Magnification of Compound Microscope
Various types of lighting used in a compound microscope include the natural white light referred to as bright field lighting; phase contrast and dark field lighting.
Procedure:
- Place the specimen slide in the middle of the stage and clamp it using stage clips.
- The slide must be positioned in the middle of the objective lens.
- While looking through the eyepiece, adjust the diaphragm and mirror to get the desired intensity of light illuminating the specimen.
- Adjust the body tube with the help of the coarse adjustment to get a clear focus of the specimen under study.
- The shift to high power resolution and again adjust to get the clear image of the specimen and observe.
Pictures of specimen observed through compound microscope:
Pinus Pollen Grains:
Sand:
Salt:
Hair:
Precautions
- Always hold the microscope by the stand. Never hold it through the eyepiece.
- Ensure that the stage and the lenses are clean before and after using the microscope.
- Lens of the microscope should be cleaned using lens paper only.
- Excessive force should not be applied against the movable parts of the instrument.
- Always begin viewing the specimen by using the lowest power objective. This is called as the scanning power.
- Remember to return to scanning power before removing the slide from the microscope.
Overview:
The present experiment aims to acquaint students with the different parts of the compound microscope. The discovery of the microscope has enabled humans to view what was invisible few decades ago. The advancement in the field of cytology, cytogenetics, microbiology, histology and anatomy can be attributed to this important discovery.
Compound microscopes are quite complex and allow the users to see objects that are as small as 1 µm. These microscopes are typically used to study animal and plant cells which are in the range of 10 to 100 µm in size. Various uses of a compound microscope include the examination of Bacteria in living state or after fixation and staining. The arrangement, motility, and the approximate size of the organisms can be observed through the examination of wet films or ‘hanging drops’.
