Figure 1.10. The spectral response curve for healthy vegetation has a "peak and valley" trait. Chlorophyll in leaves absorb energy in the blue and red visible light wavelengths, but reflects green light, hence vegetation is green.
But vegetation strongly reflects EM radiation in the near-infrared wavelength. The steep rise in the vegetation spectral curve is called the "red edge".
At 1.4, 1.9 and 2.7 EM radiation is absorbed by the water in the leaf structure. Thus, the water more content in vegetation, the lower the amount of EM radiation reflected.