What is the portion of radiant energy that can be seen by the human eye?

The portion of radiant energy that can be seen by the human eye is known as visible light. This segment of the electromagnetic spectrum includes wavelengths roughly between 400 to 700 nanometers. It encompasses all the colors that we perceive, from violet to red. When visible light from various sources interacts with objects, it can be absorbed, reflected, or transmitted, which allows us to perceive the colors and brightness of those objects.

Infrared light, while part of the electromagnetic spectrum, falls outside the visible range and is primarily perceived as heat rather than light. Ultraviolet light is also invisible to the human eye and has shorter wavelengths than visible light, while X-rays have even shorter wavelengths and are used in medical imaging but are not detectable by human vision. Understanding the characteristics and range of light in the electromagnetic spectrum helps clarify why visible light is the correct answer here.