Question

Which of the following materials is not lustrous?

• A. Gold
• B. Silver
• C. Wood
• D. Diamond

Answer 1

The correct option is C

Wood

Explanation for incorrect options:

1. Metals are lustrous because they contain free electrons.
2. The free electrons in the metal can move freely, reflecting any light that strikes them.
3. Because this is a specular reflection rather than a diffused reflection, the metal surface appears shiny or lustrous.
4. Lustrous refers to something that is shiny and bright.

Hence, options (A), (B), and (D) are incorrect.

Explanation for correct option:

1. When a parallel light beam reaches a rough surface, the light rays are reflected in various directions, or the light rays are dispersed, it is known as irregular reflection.
2. When the light falls on the materials made of wood, the light is reflected in a diffused or irregular manner.
3. Hence, wood is not lustrous.

Hence, option (C) is correct.