This article describes our efforts to make variable focal length lenses using gelatin for use in physics instruction.The lens mold is made of half-sphere silicone baking molds for cooking, and the lens mount is made of laminating film, and the variable focal length lens was reproduced to be elastic like a human lens. By manipulating the mount, the focal length can be changed within a range of 3.7–5.4 cm. Gelatin variable focal length lenses are expected to be of high educational use due to the ease of acquisition of materials in daily life, ease of making and operation of lenses and mounts, and safety.
The crystalline lens of the eye is a variable focal length lens. When looking at an object, the eye lens changes the radius of curvature of the lens through the contraction and relaxation of the ciliary body, and the focal length also changes accordingly. Therefore, even...