The eye is one of the many marvels of the human body. The colored iris of the eye, surrounding the pupil, acts as a diaphragm to keep the amount of light entering the eye fairly constant. If you walk out the door of your house to a sunny yard, the iris opening gets smaller letting less light into your eye. If you enter a dark room after watching your favorite television program, the iris gets larger to allow more light to enter your eye. This is a protective reflex, as too much light could damage the retina, which is where the image forms in the eye, similar to the film of a traditional camera or the CCD of a digital camera. In a similar way, seeing can become difficult it too little light enters the eye. In this lesson you will use Voyager’s Light Sensor and design a Scratch program to model the behavior of the eye’s iris. The iris will expand when the intensity of the light entering the sensor decreases, and will contract when the intensity increases.
