The camera obscura is a well-known optical device in the form of a closed box with a hole in one of its walls through which light rays pass, forming an inverted image of the external objects on the opposite wall, as can be seen in Fig. 1(a). Despite the simplicity of its basic design, they have been widely used by scientists and artists. In…

A smartphone is a powerful learning aid in the hands of a large section of students around the world. The camera of the phone can be used for several learning purposes apart from its obvious purpose of photographing. If the focal length of the lens of the camera can be determined, several experiments in optics can be performed with it. In some…

In this study, we propose a novel and direct method of determining the focal length of a converging or diverging lens using a smartphone. The standard optical sensor used in modern smartphone cameras is an active-pixel sensor called the complementary metal-oxide-semiconductor (CMOS). The CMOS is covered by an assembly of five to seven camera…

We demonstrated that an optimally designed pinhole camera can be used as an astronomical tool to observe the libration and apparent diameter change of the Moon at night. The libration and apparent diameter change of the Moon were observed using a handmade pinhole camera with a diameter of 0.65 mm and a focal length of 400 mm. It was found that the…

This paper proposes a simple method to design experiments for drawing the light paths at a lens to find its effective focal length and principal planes. In the designed experiments, long-exposure photography was used to record the light scattered using a moving sheet of paper, thus revealing the light path. According to the proposed experimental…

Astrophotography has been responsible for the discovery of planets, solar systems, stars, and several other celestial objects, which directly helps with expanding our knowledge about the universe and creating scientific models for nature. Practical techniques have been extensively described, including Covington, who has published an extensive…