Experimental Study of Shadow Formation in Stellar Binoculars with a Combination of Objective and Ocular Lens Power

Abstrak

This study aims to analyze the formation of shadows in simple stellar binoculars by varying the power of objective lenses and eyepieces. The focus of this study is to determine the effect of lens power variations on the clarity, sharpness, and magnification of the formed shadows, as well as to identify the most effective combination of lens power to produce optimal images. The research was carried out at the Physics Education Laboratory in October 2025 using a quantitative approach through direct experiments. The research instruments include +200 diopter objective lenses, +100 and +50 diopter eyepieces, light sources, observer screens, lens holders, and distance measuring devices. Data was collected through direct observation and magnification measurements as well as shadow clarity assessments using the Likert scoring scale. The results showed that eyepieces with less power (+50 D) produced sharper and more stable shadows, while lenses with greater power (+100 D) provided higher magnification but with reduced focus stability and internal reflections. These findings reinforce the basic optical theory regarding the relationship of objective and ocular lens focal length to shadow formation. The novelty of this research lies in the application of lens power combinations in the context of educational experiments that are simple, cheap, and easy to do. The implications of this research contribute to improving the quality of physics learning, especially in the understanding of optical concepts and the application of contextual practicum in the educational environment.