Silicon is one of the Group IV semiconductors and has an energy gap of 1.12 eV. Generally only metals have highly shiny surface, yet as shown in the figure, silicon appears to reflect like a metal. This is because
A) silicon is a good semiconductor with a well defined energy gap.
B) visible light has energies in the range 2-3 eV which is much larger than the energy gap allowing electrons to be promoted from the valence band to the conduction band.
C) the surface of silicon is smooth making it reflect like a metal.
D) silicon can be grown in very high purity. It is the impurities that make a semiconductor dull looking.
E) None of these is correct.

Question

Silicon is one of the Group IV semiconductors and has an energy gap of 1.12 eV. Generally only metals have highly shiny surface, yet as shown in the figure, silicon appears to reflect like a metal. This is because 
A) silicon is a good semiconductor with a well defined energy gap. 
B) visible light has energies in the range 2-3 eV which is much larger than the energy gap allowing electrons to be promoted from the valence band to the conduction band. 
C) the surface of silicon is smooth making it reflect like a metal. 
D) silicon can be grown in very high purity. It is the impurities that make a semiconductor dull looking. 
E) None of these is correct.

Quizplus · Accepted Answer

The reason silicon appears to reflect like a metal is that visible light has energies in the range 2-3 eV which is much larger than the energy gap of silicon, allowing electrons to be promoted from the valence band to the conduction band. This results in the absorption of some of the incident light, and reflection of the remaining light, giving the surface a shiny appearance similar to that of a metal. The other choices are not relevant to the explanation of this phenomenon.

Silicon Is One of the Group IV Semiconductors and Has