Certified Paraoptometric (CPO) Practice Exam 2025

True or False: One prism diopter bends a ray of light 1 centimeter for every 1 meter of distance.

1. True

2. False

3. Only for angles less than 10 degrees

4. Depends on the lens thickness

The correct answer is: True

The statement that one prism diopter bends a ray of light 1 centimeter for every 1 meter of distance is indeed correct. This definition arises from the way prisms function in optics. A prism diopter is a unit of measurement that quantifies the angle of deviation produced by a prism when light passes through it. Specifically, one prism diopter results in a deviation of 1 centimeter at a distance of 1 meter from the prism's apex. This linear relationship holds consistently within typical usage scenarios in optometry. The other options present scenarios that may add complexity not relevant to the straightforward definition of a prism diopter. For instance, the mention of angles less than 10 degrees introduces unnecessary limitations, as the fundamental definition remains valid across a range of angles within practical applications, despite potential deviations in specific cases. Non-uniformity due to lens thickness is another factor that can complicate optics, but for a pure prism setup, the standard measurement remains stable. Therefore, acknowledging the correct definition leads to understanding the basic principle behind prism diopter measurements.