Action spectrum

Action Spectrum is a graphical representation of the physiological activity plotted against the wavelength of light. It shows which wavelength of light is most effectively used in a specific chemical reaction. Some reactions are more effective at specific wavelengths of light compared to others.

An action spectrum is the rate of a physiological activity derived from absorption spectrum of a pigmented molecule involved in the activity plotted against wavelength. The action spectrum depicts the efficiency of electromagnetic radiation in driving a particular process.

History

The concept of the action spectrum was first introduced by T.W. Engelmann in 1882. Engelmann used a prism to separate the different wavelengths of light, and then exposed different segments of a filamentous alga to the different wavelengths. He observed that the most oxygen bubbles were produced in the blue and red light, indicating higher photosynthetic activity. This experiment was the first to demonstrate the action spectrum of photosynthesis and led to the discovery of the photosynthetically active radiation region of the light spectrum.

Applications

Action spectra are used in various fields such as biology, chemistry, and physics. In biology, they are used to identify the wavelengths of light that drive photosynthesis. In chemistry, they are used to study the reactions driven by light, such as photolysis and photoisomerization. In physics, they are used to study the interaction of light with matter.

See also

• Absorption spectrum
• Emission spectrum
• Spectral line
• Spectral power distributions