What type of light source emits its own light, making it visible to the human eye?

A luminous light source is one that emits its own light. This characteristic is fundamental in defining what makes a source luminous, as it does not rely on external light to be visible. Common examples of luminous sources include the sun, light bulbs, and fire. These sources can be detected directly by the human eye due to the light they produce themselves.

In contrast, reflective sources do not produce their own light but rather reflect light from other luminous sources, which is why they can only be seen when illuminated. Translucent materials allow some light to pass through but scatter it, preventing the transmission of clear images. Opaque materials do not allow light to pass through at all, meaning they cannot be seen through and do not emit any light themselves. Thus, when determining which type of light source can be seen directly because it generates its own illumination, the luminous source stands out as the correct choice.