Phase contrast microscopy (PCM) counts those fibers that are at least how many microns in width?

Phase contrast microscopy (PCM) counts those fibers that are at least how many microns in width?

• A. 1 micron
• B. 5 microns
• C. 10 microns
• D. 15 microns

Answer: (B)

Phase contrast microscopy counts fibers that are wide enough to be seen as distinct fibers with this optical method. In practice, that means counting fibers with a width of about 5 micrometers or greater. This 5 µm threshold comes from the resolution limits of light-based viewing and the need for consistent, repeatable counts. Fibers thinner than this are not reliably detected by PCM, so they’re not included in the count. TEM can detect smaller fibers and provide more detail, but PCM is a quicker screening method that uses this 5 µm cut-off.

Phase contrast microscopy counts fibers that are wide enough to be seen as distinct fibers with this optical method. In practice, that means counting fibers with a width of about 5 micrometers or greater. This 5 µm threshold comes from the resolution limits of light-based viewing and the need for consistent, repeatable counts. Fibers thinner than this are not reliably detected by PCM, so they’re not included in the count. TEM can detect smaller fibers and provide more detail, but PCM is a quicker screening method that uses this 5 µm cut-off.