TeXes Science Practice Test 2026 - Free Science Exam Practice Questions and Study Guide

The equation for calculating magnification using a simple magnifier, indicated as Mα, is derived from the focal length (f) of the lens and relates to how the magnifier enlarges the appearance of an object. The correct equation is Mα = 25/f + 1.

In this equation, "25" represents a standard measurement in centimeters, specifically the near point distance for a typical human eye, which is about 25 cm. The term "f" is the focal length of the magnifier. The equation indicates that as the focal length decreases (meaning the lens becomes more powerful), the magnification increases, because the term 25/f grows larger.

This relationship is essential in optics to understand how simple lenses enhance our ability to see details. The "+1" accounts for the fact that the lens does not only magnify an image but also shifts the apparent location of the image closer to our eyes, thereby allowing for a more comfortable viewing experience without straining our vision.

The other options present variations that do not accurately reflect the relationship between focal length and magnification in the context of a simple magnifier. They either misplace the terms or provide incorrect mathematical relationships that do not conform to optical principles related to magnification.