Wavelengths Lecture

The last discussion involved the absorption spectrum related to photosynthesis.
Definition: An absorption spectrum shows which visible light wavelengths are absorbed by pigments during photosynthesis.
Chlorophyll a:
- Main pigment in photosynthesis.
- Peaks in blue-violet and around 680 nm.
Chlorophyll b:
- Accessory pigment assisting in energy absorption.
- Absorbs light at different wavelengths; peak around 650 nm.
Carotenoids:
- Provide additional support for photosynthesis; act as accessory pigments.
- Related to essential nutrients like vitamin A.

Definition: Indicates regions of the visible light spectrum that support photosynthesis.
It shows where photosynthesis occurs, not just the absorption of light.
Measurement Methods:
- Liberation of oxygen or consumption of carbon dioxide can measure photosynthesis rates.

Conducted a crucial experiment to establish the action spectrum for photosynthesis without O2 sensors.
Method:
- Used filamentous algae exposed to white light separated into specific wavelengths using a prism.
- Incubated algae with aerobic bacteria that consume oxygen.
Results:
- Bacteria accumulated in regions where the algae produced oxygen, showcasing photosynthesis in action.

Plants often appear green due to the reflection of green light, not absorption.
Chlorophyll absorbs primarily in the blue-violet and red ranges; reflects green light.
Example with Carotenoids:
- Carrots appear orange due to carotenoids; they absorb green and some blue-violet light, reflecting orange.

Hemoglobin in red blood cells appears red due to reflected light.
Absorbs mainly blue-violet light (400 to 520 nm) and reflects red wavelengths, contributing to its coloration.
Emphasizes the relationship between absorption and the colors that we perceive.