Light – Reflection and Refraction

Which one of the following materials cannot be used to make a lens?

1. Water
2. Plastic
3. Glass
4. Clay

Solution:

Lenses can be made from transparent material. Clay is an opaque material, whereas water and glass are transparent materials. One may think of how plastic can be used to make a lens. Certain types of plastic can be transparent, and hence, we can create a lens out of them. One may wonder how water can be used to make a lens. Did you ever see a fish bowl, which is almost spherical in shape? When you look through the bowl filled with water, you observe that distant objects on the other side of the bowl appeared inverted. Thus , the water in the bowl acts like a convex lens.