MICROSCOPY • OPERATION OF A BRIGHTFIELD MICROSCOPE

What is the total magnification of a specimen using the 40X objective?

Total magnification is 400X.

Total magnification

Total magnification is the overall enlargement of the image of a specimen. To calculate total magnification, multiply the magnification of the ocular lens (10X) with the magnification of the objective lens.

Histology

histology is study of tissue

Which of the three factors affecting image quality is altered by the light source?

Contrast can be altered by light intensity and staining.

Contrast

Contrast refers to the ability to distinguish objects, such as cells, from the background

Cytology

cytology is study of cells

Often what you want to visualize is not in the middle of the field of view and you must move the slide around to find what you want to study. To move the slide, you move the stage. As you look at the microscope the stage knob on the top moves the stage forward and back. The stage knob on the bottom moves the stage side to side.

--Additional adjustments to the microscope can be made regarding lighting. These fine adjustments will not be addressed in this simulation. ----As magnification of the image increases, the light intensity decreases and will have to be adjusted. ----The condenser lens focuses the light on the slide. ----The sliding bar on the condenser lens is the aperture. As you move the aperture to decrease the light to the slide, the contrast increases. As you move the aperture to increase the light to the slide, the contrast decreases.

There are three factors that determine the quality of a microscopic image:

Magnification Resolution Contrast

Magnification

Magnification is the apparent increase in image size.

Resolution

Resolution is the ability to distinguish fine detail.

How do the coarse and fine focus knobs work on a bright field microscope?

The focus knobs move the stage up and down, allowing the user to move the slide into focus.

Key Concepts

The goal of microscopy is to create a magnified image of objects too small to be seen with the eye alone. Brightfield microscopes use a combination of glass lenses and light to view the specimen. Microscopes are often used to study bacteria, cells, and tissues. Fields of study where a

The field of view

The microscope you are using has four objective lenses to magnify the image: 4X, 10X, 40X, and 100X. When focusing on a slide, start on the scanning, or low power, objective lens. The lower the power objective, the greater the field of view. The field of view is the amount of the slide you are able to see through the eyepiece.

Pathology

pathology is study of disease

What is the advantage of starting with the 4X objective before moving to the 10X and then the 40X objective?

the field of view is larger, and it is easier to focus

Why should the fine focus knob typically be used with the 10X and 40X objective lenses?

the slide should be close to in focus after focusing at the 4x objective. focusing with the coarse focus knob would result in too large a change in focus