National League for Nursing (NLN PAX) Practice Exam

The approximate focal length of a thin converging lens can be directly obtained by the student through practical experimentation. When a converging lens is used, it focuses parallel rays of light (such as sunlight) to a point called the focal point. Many experiments involve directing sunlight through the lens and observing where the light converges. By measuring the distance from the lens to the point where the image of the sun is sharply focused, the student can determine the focal length. This measurement is straightforward and can be conducted with basic measuring tools, making it a directly obtainable quantity.

The other options, while related to the experiment, do not provide a direct measurement in the same way. The diameter of the lens can be measured, but it does not yield information specific to the optical properties of the lens itself. Measuring the intensity of sunlight involves more complex tools and calculations, as it encompasses how much light is received over an area rather than specific focal properties of the lens. Similarly, measuring heat produced by sunlight requires different equipment and does not correlate directly to the lens's function or characteristics as effectively as focal length does. Thus, the focal length is the most relevant and directly measurable aspect in this experimental context.