Calibration

Calibration 

• ensures that the measurements you take using the ocular micrometer (the ruler in the eyepiece) are accurate.

Ocular micrometer - the ruler in the eyepiece.

Stage micrometer -  slide with a ruler, typically 1,000 micrometers (µm) long, with 100 divisions, each division representing 10 µm.

Calibration values

• 4X lens: 1 ocular division = 25 µm.

• 10X lens: 1 ocular division = 10 µm.

• 40X lens: 1 ocular division = 2.5 µm.

Note: These values are consistent unless the lenses are changed.

• Resolution: the ability of an optical microscope to distinguish between two closely spaced points as separate entities. Better resolution allows finer details to be observed.

• Light and Magnification: Objects appear dimmer at higher magnification because the field of view is smaller, meaning less light reaches the eye. Therefore, more light may be needed at higher magnifications.

• Depth of Field: refers to the range of the specimen that remains in focus at one time.

• At low magnification, the depth of field is longer, so more of the specimen (such as a set of threads) appears in focus, making it hard to distinguish the order of layers.

At high magnification, the depth of field decreases, allowing you to focus on individual layers, such as distinguishing the top thread from the bottom thread on a slide.