The subprime mortgage crisis was caused by hedge funds, banks, and insurance companies. The first two created mortgage-backed securities. The insurance companies covered them with credit default swaps. Demand for mortgages led to an asset bubble in housing.
The field of dielectrics is a branch of physics that covers how insulating materials separate different electrical charges in a capacitor. A capacitor is a device with two metal plates of opposite charges, with a dielectric insulating material in between the keeps the charges separate.
If a dielectric material does not include light-absorbent additive molecules (pigments, dyes, colorants), it is usually transparent to the spectrum of visible light. Color centers (or dye molecules, or dopants) in a dielectric absorb a portion of the incoming light wave.