The world is full of colors. Most of the colors we see around us can be created on common digital displays simply by superposing light with three different wavelengths. However, no mixture of colors can produce a fully pure color identical to a spectral color. Using a smartphone, students can investigate the main features of primary color addition and understand how colors are made on digital displays.
When a stethoscope is placed on the chest over the heart, sounds coming from the heart can be directly heard. These sound vibrations can be captured through a microphone and the electrical signals from the transducer can be processed and plotted in a phonocardiogram. Students can easily use a microphone and smartphone to capture and analyse characteristic heart sounds. Since smartphones are commonplace and require only inexpensive supplementary equipment, the experiments can be carried out by the students themselves. This allows for the separation of the class into small groups and into experimental homework assignments, so that the students can carry out measurements with less ambient noise.
Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole glasses really give better vision? Some ways to use this question for motivation in teaching optics have been discussed.1 For this column we include a series of experiments that students can complete using a model of the eye and demonstrate issues related to pinhole vision correction.
We describe a model of the human eye that incorporates a variable converging lens. The model can be easily constructed by students with low-cost materials. It shows in a comprehensible way the functionality of the eye's optical system. Images of near and far objects can be focused. Also, the defects of near and farsighted eyes can be demonstrated.
A simple device is used to show both the wave aberration emerging from an eye model and the basic principles of measuring wavefront aberration with a Hartmann-Shack aberrometer.
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