Studying a Model of Human Eyes by Adjustable Liquid Lens

In this research, an adjustable liquid lens whose focal length is adjustable by changing the volume of the
water within the lens was designed and constructed. The biconvex lens was made from two pieces of food
preservation lids and an elastic sheet of polymer. The frame of the lens was made by connecting the lids
on their rims which were sealed with a waterproof polymer sealant. To calibrate the lens, it is crucial to
determine the relationship between the amount of water within the lens and the focal length. Three different
techniques were used to find the focal length of the lens. In the first technique, the focal length was calculated
using Lensmaker’s equation based on the geometry of the lens. The focal length, in the second technique,
was determined using the object and image distances. The last technique was calculated using the equation
given in the Newtonian form. It was found that the focal lengths obtained from three different methods were
in good agreement for a given volume of water. The polynomial equation of degree two was used to fit the
data between the volume of water within the lens and the focal length. The data were strongly correlated
with the value of R-squared of approximately 1.00. Therefore, it is suitable to be used to create a classroom
demonstration set on the topic of human vision, including normal vision, hyperopia and myopia, was
provided.