Question

1. Copy the main parts of a microscope and their function

1. How do we calculate the diameter of a field of view at a magnification “A”, if we know the diameter of a field of view at a magnification “B”

Answer 1

There are three structural parts of the microscope i.e. head, base, and arm.

1. Head – This is also known as the body, it carries the optical parts in the upper part of the microscope.
2. Base – It acts as microscopes support. It also carriers the microscopic illuminators.
3. Arms – This is the part connecting the base and to the head and the eyepiece tube to the base of the microscope.

The optical parts of the microscope are used to view, magnify, and produce an image from a specimen placed on a slide. These parts include:

1. Eyepiece – also known as the ocular. this is the part used to look through the microscope. Its standard magnification is 10x with an optional eyepiece having magnifications from 5X – 30X.
2. Eyepiece tube – its the eyepiece holder. It carries the eyepiece just above the objective lens. In some microscopes such as the binoculars, the eyepiece tube is flexible and can be rotated for maximum visualization, for variance in distance.
3. Objective lenses – These are the major lenses used for specimen visualization. They have a magnification power of 40x-100X. There are about 1- 4 objective lenses placed on one microscope.
4. Nose piece – also known as the revolving turret. It holds the objective lenses. It is movable hence it cal revolve the objective lenses depending on the magnification power of the lens.
5. The Adjustment knobs – These are knobs that are used to focus the microscope. There are two types of adjustment knobs i.e fine adjustment knobs and the coarse adjustment knobs.
6. Stage – This is the section on which the specimen is placed for viewing. They have stage clips hold the specimen slides in place.
7. Aperture – This is a hole on the microscope stage, through which the transmitted light from the source reaches the stage.
8. Microscopic illuminator – This is the microscopes light source, located at the base. It is used instead of a mirror.
9. Condenser – These are lenses that are used to collect and focus light from the illuminator into the specimen.They play a major role in ensuring clear sharp images are produced with a high magnification of 400X and above.
10. Diaphragm – its also known as the iris. Its found under the stage of the microscope and its primary role is to control the amount of light that reaches the specimen. Its an adjustable apparatus, hence controlling the light intensity and the size of the beam of light that reaches specimen.​

The field of view is the circular area under observation when using a microscope. Diameter of the field of view should be known to calculate the size of the specimen you are looking at. All you need to calculate the field diameter is a slide with a millimetre grid or ruler mounted on it.

Instructions

1. Mount the mm slide on low power, focus it and measure the field diameter. Remove the slide from the stage.
2. The ratio of magnification, M, to diameter, D, is the same at every magnification. Using the measured diameter from step 1, D1, calculate the diameter of the field of view (Dx), at other magnifications (Mx), using this formula:

For example, if the magnification of your ocular lens is 10X and your objective lenses are 4X, 10X and 40X, the field diameters will be 4.2mm, 1.7mm and 0.42mm on low, medium and high power respectively.

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