What does the objective lens do on a microscope?

Objective lenses collect the light passing through the specimen and focus the light beam to form a magnified image.

Objective lenses are the primary optical lenses for specimen visualization on a microscope. Objective lenses collect the light passing through the specimen and focus the light beam to form a magnified image. The objective lenses are the most important parts of a microscope.

compound-microscope-part

How to calculate the magnification power?

To obtain the total magnification power, multiply the magnification of the eyepiece and objective lens used:

For example:
[10x eyepiece] x [40x objective] = 400x total magnification

50x-to-1000x-field-of-view

[In this figure] The same specimen field of view from low to high magnifications.
At low magnifications (5x and 10x), you can have the overall view of the entire specimen – Vicia (pea family) root tip. By getting closer (with higher magnification), you will start to notice the cells and their nuclei (blue dots). At high magnifications (63x and 100x with lens immersion oil), you can see some nuclei looked different from others. These spindle-shaped nuclei are dividing (or under mitosis) and their chromosomes (bundles of DNA) are moving apart.


Extended read:

what is microscope cover

What is a Microscope? Function and Magnification

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