Explain Light in cell Metabolism?

Energy for almost all organisms on earth is derived directly or indirectly from light energy produced by the sun. Sunlight consists of energy packets called photons that travel in waves of various lengths.

Wavelength refers to the distance between the peak of one wave to the peak of the next wave. We see light as different colors depending upon the wavelength of the light our eyes receive. Light containing visible light of all wavelengths appears white. The shorter the wavelength of light, the more energy it has. The energetic ultraviolet rays are shorter than 400 nm; infrared rays are longer than 700 nm.

White light contains all of the wavelengths of light. When white light strikes an object, substances called pigments absorb certain wavelengths and reflect others. Objects appear the color of the reflected light. So, if an object appears to our eyes as red, the pigment in the object is absorbing all of the other colors (wavelengths) except red, and only red wavelengths are reflected to our eyes!

A graph of absorption measured against wavelength for a given pigment is called an absorption spectrum. An action spectrum is a graph of photosynthesis rates for different wavelengths of incident light for a given pigment.