Photosynthesis

Think of all of the noises you can hear in the world.  Some are very loud, some are very quiet, and most are in between, at a talking volume.  However, there are sounds that are both too high and too low in frequency to hear, and the same happens with light.

 

The electromagnetic spectrum is the entire range of light, and just as we can only hear the middle range of sounds, we can only see the middle range of light.  Infrared light is too low energy for us to visibly see, and ultraviolet is so high energy that we cannot see it and it can be harmful to us.  The visible light spectrum is the middle range of light that we can see, from about 380nm to 760nm.  Gamma rays are incredibly short bursts of electromagnetic radiation.  At the other end of the electromagnetic spectrum are radio waves, which have incredibly long wavelengths. The light that plants use 680nm and 700nm wavelength light to perform photosynthesis.  This can be thought of a musician using specific notes to write a musical piece.  The musician uses the notes that sound the best, which is accredited to their wavelengths, just as the plants use light with wavelengths that best excite the electrons in Photosystems I and II.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The reason for only being able to see a portion of the electromagnetic spectrum is because of the energy levels of the different wavelengths of light.  For us to see light, electrons in our eyes must be excited to stimulate an electrical current that our brain then interprets.  Infrared light and anything with lower energy does not have enough energy to excite the electrons required, so we cannot see it.  Ultraviolet light is so high-energy that it damages our eyes.  See the next page for how plants use photosynthetic pigments and their relation to the visible light spectrum.