Yellow is composed of red and green light. This combination is achieved through the additive color model, which is used in the context of light. When red and green light are combined, they produce yellow light, which is perceived as yellow to the human eye. This principle is fundamental in the field of color science and is utilized in various applications, such as in the production of light-emitting diodes (LEDs) and in the understanding of color perception.

The reason for this composition lies in the way human eyes perceive light. The retina contains photoreceptor cells called cones, which are sensitive to different wavelengths of light. There are three types of cones, each sensitive to red, green, or blue light. When red and green light are combined, the cones that are sensitive to these wavelengths are stimulated simultaneously, leading to the perception of yellow. This is because the brain interprets the combined signals from the red and green cones as yellow.

According to research conducted by the National Institute of Standards and Technology (NIST), the color yellow is produced by a combination of red and green light with wavelengths of approximately 570 to 590 nanometers. This range corresponds to the overlap between the red and green spectral regions. The specific wavelengths can vary slightly depending on the source of the light and the observer's color perception.

In summary, yellow is composed of red and green light, which is a result of the additive color model and the way human eyes perceive light. This understanding is crucial in various scientific and technological applications, such as in the design of lighting systems and in the study of color perception.