Photometry is the measurement of visible light as perceived by the human eye. Photometry is a name formed by combining the words photo and metry. Photo is a prefix meaning light. Metry refers to the process of measurement.
Light consists of small packets of energy called photons. Light energy is a form of electromagnetic radiation and is the only form of energy visible to the human eye. Light energy travels in waves and is very fast. The sun, stars, lamps, lasers, and hot objects are examples of light...
Although common grow lights emit blue and red light, these lamps come in many different color combinations. Because each color has different effects on the plant. So, what color light is useful in plant growth?