Absorption Spectra

1
Science is facts just as houses are made of
stone, so is science made of facts but a pile of
stones is not a house, and a collection of facts
is not necessarily science. Jules Henri Poincaré
(1854-1912) French mathematician.
Absorption Spectra of Chlorophyll
2
Electromagnetic Spectrum
3
Measuring Light

• Irradiance measure of the amount of energy
  falling on a flat surface (amount per unity area)
• Intensity the amount of light leaving a light
  source
• Photon particle of light
• Quanta energy in a photon
• PPFD Photosynthetic Photon Flux Density (amount
  per unit area)
• PAR photosynthetically active radiation
• (350nm-700nm)

4
Measuring light

• Photometric
• Based on our eyes ability to detect
  electromagnetic radiation
• Units are foot-candles (fc) or lumens m-2 (lux)

5
Measuring light

• Radiometric
• Based on actual spectral distribution
• Units are
• Energy W m-2
• Number of Photons umole-m-2-s-1

Why do physiologists like photons?
6
Photosynthesis 1. Conversion of light energy
to chemical energy. 2. Short term storage of
chemical energy. 3. Long term storage of
chemical energy.
7
Basic principle of Photo-Chemistry
One photon-------One Excitation
8
Absorption Spectra of Chlorophyll
9
(No Transcript)
10
Questions to answer using figure 1.

• What is the effect of the atmosphere on direct
  sunlight?
• Look at the Direct Sunlight at Sea Level line.
  What causes all the dips in the infra-red?
• What colors (wavelengths) of light are
  selectively adsorbed by clouds?
• What color is sky light?
• Can you tell from this graph why leaves are
  green?
• What is the significance of the lack of
  absorbance of infra-red radiation by vegetation?

11
(No Transcript)
12
http//www.youtube.com/profile?usergreatpacificme
diap/u/58/D6tbOBhbOZU