Which of the following is true about the PCM eyepiece magnification?

• A. It is 5x
• B. It is 10x
• C. It is 15x
• D. It is 20x

Answer: (B)

In PCM counting, total magnification is essential because it determines how clearly fibers stand out and how accurately you can identify and count them. The eyepiece used with PCM is 10x, and with a typical 40x objective this gives you a total magnification of 400x, which is the standard requirement for PCM fiber counting. This setup provides a good balance between a wide enough field of view to locate fibers and enough detail to distinguish fibers from other particles. If the eyepiece were higher, say 15x or 20x, the total magnification would become 600x or 800x, shrinking the field of view and making counting slower and potentially less consistent. If the eyepiece were lower, like 5x, the total magnification would drop to 200x, reducing resolution and making accurate identification harder. So the PCM eyepiece is 10x because it supports the standard 400x magnification needed for reliable counting.