How Does Chlorophyll Glow?
Chlorophyll doesn't glow in the same way a lightbulb does; instead, it fluoresces. This means it absorbs high-energy light, like ultraviolet (UV) light, and then re-emits this energy as lower-energy light, which we often see as a red glow. This process is called chlorophyll fluorescence.
The process begins when chlorophyll absorbs light energy. This energy excites electrons within the chlorophyll molecule to a higher energy level. These excited electrons are unstable and quickly return to their original, lower energy state. As they do so, they release the excess energy as light, typically in the red region of the visible spectrum. Sometimes, excess energy is released as heat.
Several sources corroborate this explanation:
- Fluorescence: One source explicitly states, "Chlorophyll fluoresces to release the extra energy as red light." [Reference: Unattributed text provided]
- UV Light Excitation: Another source explains that when UV light interacts with a chlorophyll solution, "electrons are promoted from the S0 state to the S2 state," leading to fluorescence. [Reference: Fluorescence of chlorophyll with UV light | MSU SMACS]
- Red Fluorescence: Multiple sources describe chlorophyll exhibiting red fluorescence under UV or blue light excitation. [References: Chlorophyll under UV-light : r/Biochemistry; P51™ Lighting up Chlorophyll – miniPCR bio; Green Plants, Red Glow | NSTA]
- Algae and Plants: Experiments using algae and plant leaves demonstrate similar fluorescence patterns, concluding that algae also contain chlorophyll. [Reference: Activity - Know by the Glow - American Chemical Society]
Practical Examples
- Extracted Chlorophyll: Extracting chlorophyll from leaves and exposing it to UV or blue light will cause it to fluoresce red. [References: Chlorophyll Fluorescence - How to isolate chlorophyll and make it ..., P51™ Chlorophyll Lab: A Free Resource – miniPCR bio]
- Intact Plants: While less visible, intact plants also exhibit chlorophyll fluorescence, a phenomenon used to study photosynthesis. [Reference: How Does Your Garden Glow? NASA's OCO-2 Seeks Answer ...]
Why the Red Glow?
Chlorophyll absorbs strongly in the blue and red regions of the visible spectrum, appearing green because it reflects green light. When it fluoresces, it releases energy at a longer wavelength (lower energy), explaining the red glow. [Reference: Bloody Chlorophyll]
