Microscopy: Focusing, Slides, and Cell Structures

A student is observing a specimen under a microscope at 400x total magnification. They switch to a 100x objective lens to get an overview of a larger area of the slide. What happens to the field of view?

A microscope has an ocular lens of 10x and an objective lens of 40x. If a student replaces the 40x objective lens with a 100x objective lens, what is the new total magnification?

Which of the following best describes the function of the iris diaphragm lever on a microscope?

A student is using a microscope to observe cells and notices that only a very thin slice of the specimen is in focus at any one time. What is this property of the microscope called, and how is it affected by increasing magnification?

A student measures the diameter of the field of view under a microscope at 40x magnification to be 4mm. If they switch to 100x magnification, what will be the approximate diameter of the field of view, assuming everything else remains constant?

Fine Adjustment Knob

Wet Mount vs. Permanent Slide

Field of View Change

Plant vs. Animal Cell

Fine adjustment knob is for precise focusing, especially at high magnification
Coarse adjustment knob is for large-scale focusing at low magnification
Wet mount is a temporary slide preparation using a liquid, while a permanent slide is fixed and preserved
As magnification increases, the field of view decreases
Total magnification is calculated by multiplying the objective lens magnification by the ocular lens magnification
Resolution is the ability to distinguish between two closely adjacent points
- Resolution decreases, as magnification increases
Depth of focus is the thickness of the specimen that is in focus at one time
- Depth of focus decreases, as magnification increases
Plant cells have cell walls and chloroplasts
Animal cells lack cell walls and chloroplasts
Field of view (FOV) is the diameter of the circle you see when looking through a microscope
To calculate FOV:
- Measure FOV at low power using a ruler
- Use the formula: FOVlow x Maglow = FOVhigh x Maghigh to calculate FOV at higher magnifications
To estimate size of an object:
- Estimate how many objects can fit across the field of view
- Divide the field of view diameter by the number of objects
Iris Diaphragm Lever: Controls the amount of light passing through the specimen
Condenser: Focuses light onto the specimen
Objective Lens: Primary magnification of the specimen (4x, 10x, 40x, 100x)
Ocular Lens: Further magnifies the image (usually 10x)
Conversions:
- 1 meter (m) = 100 centimeters (cm)
- 1 centimeter (cm) = 10 millimeters (mm)
- 1 millimeter (mm) = 1000 micrometers (µm)
- 1 micrometer (µm) = 1000 nanometers (nm)

Learn about fine and coarse adjustment knobs for focusing microscopes. Understand wet mount vs. permanent slides. Explore magnification, field of view, resolution, and depth of focus, and distinguish between plant and animal cells.