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

Question

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

1. A. Water
2. B. Plastic
3. C. Glass
4. D. Clay (Correct answer)

Correct Answer

Option D — Clay

Detailed Solution & Explanation

The correct answer is Clay.

Key Points

• A lens must be made of a transparent material so that light can pass through and be refracted.
• Glass, plastic and even water are transparent and can form lenses; clay is opaque and cannot.

Additional Information

• A water lens can be demonstrated with a drop of water on a flat surface, or a water-filled round flask acting as a converging lens.
• Lenses come in two families: convex (converging), thicker at the centre, and concave (diverging), thinner at the centre.
• Convex lenses correct hypermetropia (long-sightedness) and concave lenses myopia (short-sightedness); lens power is measured in dioptres, the reciprocal of focal length in metres.