Question

Metallic lustre is due to __________
(A) High density of metals
(B) High polish on the surface of metals
(C) Reflection of light by mobile electron
(D) Chemical inertness of metals

Answer 1

Hint - To solve this question firstly we shall understand about lustre. What is lustre? Lustre in mineralogy describes how light is reflected on the surface of the mineral. It is one of the properties mineralogists look at when trying to determine the identity of a mineral. We will study all the related information about this term which will further lead us in approaching our solution.

Complete step by step solution:
> Metallic lustre- Metallic lustre is for minerals that are opaque and reflective and have look polish examples include Galena, pyrite, magnetite. Are some metallic lustre-.
> Metals have lots of free electrons. These electrons as a negatively charged form cloud in a uniform background of positive charge forming a highly polarized plasma. A plasma is just a dense of charge particles and the distribution of the charge within its volume can be changed by applying an external electromagnetic (EM) field. In the absence of any external EM field, the charges in the plasma are uniformly distributed within the metal. So, there are regions within metal that are negatively charged. Thus, incoming light creates an oscillating EM wave on the surface of metal and disturbs the plasma.

Hence the correct option is C - Reflection of light by mobile electron

Note - Basically lustre depends on the minerals reflecting power, degree of transparency and structure. Variations in these properties produce different kinds of lustre whereas variation in the quantity of reflected light produce different intensities of same lustre.