Final answer:
Sunlight wavelengths longer than 700 nanometers are considered infrared radiation and cannot be seen by humans. They have lower frequency and less energy compared to the visible spectrum.
Step-by-step explanation:
Wavelengths of sunlight that are longer than 700 nanometers fall into the category of infrared radiation. These wavelengths are too long to be seen by the human eye and therefore are not part of the visible spectrum, which ranges from approximately 400 to 700 nanometers. Infrared radiation is associated with heat, as these wavelengths are often emitted by objects that are warm. Additionally, sunlight wavelengths longer than 700 nanometers have a lower frequency than visible light and, in line with the principles of electromagnetic radiation, less energy than shorter wavelengths such as blue or green light.