Photochromic glass, which is used for sunglasses, turns darker when it is exposed to strong light and becomes more transparent again when the light is weaker. This darkening happens because silver atoms are present in the glass. The reactions below are involved. reaction 1 is: $\mathrm{Ag^+ + Cl^- \rightleftharpoons Ag + Cl}$ reaction 2 is: $\mathrm{Cu^+ + Cl \rightarrow Cu^{2+} + Cl^-}$ reaction 3 is: $\mathrm{Cu^{2+} + Ag \rightarrow Cu^+ + Ag^+}$ Which statement correctly describes these reactions?
- A$\mathrm{Cu^+}$ and $\mathrm{Cu^{2+}}$ ions act as catalysts.
- B$\mathrm{Cu^+}$ ions act as an oxidising agent in reaction 2.
- CReaction 3 increases the darkness of the glass.
- DSilver atoms are reduced in reaction 3.