Task: To know how we see with the help of light.
Required accessories: One shoe box, stone chip and some black paper.
Procedure: Take a shoe box with the cover. Wrap the inner side of the box with black paper. Make a small hole on the cover of the box and a big hole on its wall of one side of the box Keep the stone chip just below the hole of the cover. Place the cover. Close the big hole of the side wall by a thick black paper or tape. Try to see the stone chip through the small hole of the cover. Can you see the stone chip? No, it is not visible. Remove the black paper or tape from the hole on the side wall of the box. Light enters inside the box through this hole. This you try to see the stone through the hole on the cover. Is the stone visible now? Yes, it is.
Analysis: What decision we may reach from this? We can come to the decision that, nothing can be seen without light. When light falls on an object and if it is reflected back to our eyes, then we can see the object. Why the blind people cannot see. When light coming from an object and falls on normal eyes only then the object is seen. Eyes of the blinds are not normal so they cannot receive the light coming from the object to their eyes. As a result they cannot see.
How can we see the writings printed on this page? Any black body or any black writing absorbs light coming from any sources. But our eyes receive the light reflected from the white paper. As a result, we can see the printed black words from the white paper. Bright colors absorb more light than the light color. The object that absorbs all the light looks be black.