Why is exposed photographic emulsion black?

This has to do with the scattering of light. Yes, the elemental silver in developed photographic paper is present as particles, but these particles are of varying sizes and shapes. Small, spherical, uniform particles of silver can display many individual colors depending on the particle size, but in most black and white films, the developed silver more closely resembles scrunched up filaments, like steel wool. It is this unusual particle shape, as well as both disperse particle size distribution and the electrical properties of Silver, that causes the black color. To a lesser extent, the silver will oxidize on its surface as well, which is a dark color.