1. Light and Pigments

2. Properties of Light Electromagnetic energy/radiation Travels in waves
Photon
Light travels as a wave, behaves as particle
Fixed nrg quantity
Wavelength (λ)
Distance between waves
Determines NRG
NRG inversely related to wavelength
Shorter wavelength (λ) = ______ energy.
Higher

5. Light and Matter 3 types of interactions
Reflected
Light bounces off matter
Transmitted
Passes through matter
Absorbed
Light disappears from spectrum sorta
Substances absorb light = pigments

6. Spectrophotometer discussion only
Detects absorption spectrum of pigments
Uses light of different λ through a sample
Measures light transmitted
Generates light absorption vs. λ

7. Photosynthesis Pigments
Chlorophylls
Chlorophyll a
Absorbs violet blue and red
Transmits green
Chlorophyll b
Absorbs Blue light
Accessory Pigments
Carotenoids
Photoprotection
Transmits yellow and orange

9. Action Spectrum Not all colors are best for photosynthesis
Red and Blue light- absorbed and used in photosynthesis
Identified by measuring O2 release under different λ of light
Question: Why is this graph different then that of chlorophyll a or b absorbance?

12. Excited Chlorophyll! Yipee!
When a molecule absorbs a photon 1 of its e- will jump from its ground state (low NRG) to an excited state (high NRG).
Excited
state
Energy of election
Heat
Photon
(fluorescence)
Chlorophyll
molecule
Ground e–
Figure A

14. Excitation of Chlorophyll by Light
When pigment absorbs light
Goes from a ground state  excited state = unstable
Molecule can absorb photons only if there NRG matches the NRG difference between the ground state and excited stare of e-
A particular compound absorbs only photons corresponding to specific λ.
Excited
state
Energy of election
Heat
Photon
(fluorescence)
Chlorophyll
molecule
Ground e–
Figure A

15. Fluorescence If an isolated solution of chlorophyll is illuminated
It will fluoresce, giving off light and heat
Figure B