Final answer:
A real shadow is analogous to an umbra and is darker because the light source is completely obstructed, while a ghost shadow is similar to a penumbra and is lighter due to partial blockage of light, allowing indirect light to reach the area.
Step-by-step explanation:
When discussing shadows as they relate to earrings, the concepts of real shadows and ghost shadows can be compared to the phenomena of umbra and penumbra, respectively, in astronomical contexts. A real shadow is analogous to the umbra, the area where the shadow is darkest because this region is completely obstructed from the light source. In contrast, a ghost shadow could be likened to the penumbra, which is a lighter, more diffuse shadow that occurs when the source of light is only partially blocked and thus some light still reaches the area indirectly.
In the case of earrings, if they were analogized to an eclipse, the real shadow would be darker (option a), similar to the umbra during an eclipse, whereas the ghost shadow would be lighter (option d), akin to the penumbra. This is because the real shadow is cast by direct blockage of light, and the ghost shadow is a result of partial blockage, allowing for some light to filter around the object, causing a diffused, lighter shadow.