Recently I got an opportunity to demonstrate how light related experiments can be made accessible to students who are visually impaired. After we successfully demonstrated light travels in a straight line, reflection and refraction (for which I was prepared), then came the question of making observations about the shadows by the student. This really was challenging since I had no set up ready.
The experiment was to be conducted by the student to observe how the size of the shadow varies as the distance of the object from the light source varies. This can be told to the blind student, but how will it become “science” when the student does not observe it himself.
Here is what I did: Usually the experiment set up is horizontal for sighted students. I got the screen on the floor and the light source above it. I used a stool with a hole to hold up the torch, so, that became a torch stand. We used a spoon as the object so that the hand of the spoon can be fixed while the student observed the shadow of the spoon head. I tied the spoon hand to a wooden block so that it wouldn’t move during the experiment.
The screen was a Braille sheet mounted on a corrugated plastic board. The student turned on the torch. He used a light probe to differentiate between “light” and “shadow”. I helped him locate the shadow and showed how he could move the light probe to find out difference in sound. This was a little tricky because the light probe had to be held in a slant position. My student was able to identify the sound difference, but to lower the light probe to the actual point where the sound changed he needed some assistance. As teachers, we will have to look for a better set up there.
The student used a stylus to prick the position on the screen where the light probe changed the sound. Then he joined the dots to get a comparable picture of a spoon head. We repeated the experiment with a different height of the object stand.
It was now time for observations. My student observed the difference in the size of the shadow. Since he had measured the distance of the object from the light source, he could easily make the required conclusion!!