American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

How is the magnification of an object calculated?

1. Telescope distance divided by focal length

2. Tube length divided by the focal length of the lens

3. Objective power increased by eyepiece power

4. Original size multiplied by the total number of lenses

The correct answer is: Tube length divided by the focal length of the lens

The calculation of magnification in microscopy is typically defined as the ratio of the tube length, or the distance from the objective lens to the eyepiece, divided by the focal length of the objective lens being used. This relationship is fundamental in determining how much larger an object appears through the microscope compared to its actual size. In terms of practical application, this means that the longer the tube length, the greater the potential for magnification, provided that the focal length of the lens remains constant. This is especially relevant when using compound microscopes where multiple lenses are utilized. The remaining options involve concepts that do not accurately describe the magnification process in a standard manner. For instance, suggesting that the objective power is simply increased by the eyepiece power is an oversimplification and does not account for the specific mechanics of magnification. Likewise, multiplying the original size by the total number of lenses does not provide a clear or accurate method for calculating magnification, as it overlooks essential factors such as the focal lengths and arrangement of the lenses involved.