Pigment absorption spectra

Light is a range of electromagnetic waves.

Our eyes translate certain wavelengths of light into specific colors.

Colorful objects absorb certain wavelengths and reflect others.

Chlorophylls, for example, do not absorb between 500 and 600 nm and therefore they are green. They have two characteristic absorbance peaks at around 450 and 650 nm.

Carotenoids absorb a wider range of wavelengths, ranging from 400–550 nanometers (violet to green light). This causes the compounds to be yellow, orange, or red.

Phycoerythrobilin appears red because, due to the seven double bonds in its main conjugated system, it absorbs mostly green.

A graph of the solar spectrum, with light wavelength in nanometers on the x-axis and spectral irradiance in Watts per square meter times nanometers on the y-axis. The different wavelengths correspond to different colours of light. The UV portion of the spectrum is comprised of violet to blue light, with wavelength from 250 to approximately 390 nanometers.The spectral irradiance of this portion increases from around 0 to 1.2 Watts per square meter per nanometer. The next portion of the spectrum is visible light, ranging from 390 to about 700 nanometers in wavelength. At the lowest wavelenth, the light is blue, then it transitions to green, then, yellow, then orange at the end of the visible portion. This portion of the spectrum has a peak irradiance at just above 2 Watts per square meter times nanometers that corresponds to green light. Before the peak, irradiance is about 1.7 Watts per square meter times nanometers and it decreases to 1.7 Watts per square meter times nanometers after the peak. The final portion of the spectrum corresponds to infrared light, with wavelength from 700 to 2500 nanometers. The light is red in this portion of the spectrum. the irradiance starts at 1.4 and decreases to almost 0 Watts per square meter times nanometers at the end of the spectrum.

Figure 1: Solar spectrum.

Have a good look at the solar spectrum. Visible light actually comprises a narrow range of wavelengths, from about 390 to 700 nanometers!