Question

Explain the difference between lenses that are parfocal and those that are parcentric?

a) Parfocal: Lenses maintain focus when switching magnification.
b) Parcentric: Lenses keep the specimen centered during magnification changes.
c) Parfocal: Lenses maintain equal resolution across all magnifications.
d) Parcentric: Lenses ensure consistent lighting throughout magnification adjustments

Answer 1

Parfocal lenses maintain focus when changing magnification levels, while parcentric lenses keep the specimen centered when switching between different magnifications. The correct definitions are (a) for parfocal and (b) for parcentric.

Step-by-step explanation:

The difference between lenses that are parfocal and those that are parcentric is as follows:

• Parfocal lenses: These lenses maintain focus when switching between different magnifications. For example, when you change from a lower power objective to a higher power one, the image should remain nearly in focus.
• Parcentric lenses: These lenses keep the specimen approximately centered during changes in magnification. This is especially helpful for not losing track of a particular area of interest on the specimen as you increase magnification.

Thus, the correct definitions are (a) for parfocal and (b) for parcentric. The objective lens, which provides varying magnifications typical from 5x to 100x, should be parfocal to minimize the need for focus adjustments. A microscope is designed to magnify small objects with both the objective lens and the eyepiece contributing to the final magnification.