Most effective wavelength of light for photosynthesis is:

Red is the most effective wavelength of light for photosynthesis. Photosynthetic organisms (plants and algae) use the visible spectrum of light to synthesize the sugar molecules. The wavelength of visible light ranges from 380 nm to 750 nm. The visible spectrum of the light consists of violet (380–450 nm), blue (450–485 nm), cyan (485–500 nm), green (500–565 nm), yellow (565–590 nm), orange (590–625 nm) and red (625–750 nm).

The wavelength of light on which the photosynthetic activity is high is in the blue range (450–485 nm) and the red range ( 625–750 nm). All the photosynthetic organisms contain chlorophyll a pigment for photosynthesis. The chlorophyll a pigment absorbs maximum light in the blue and red wavelengths.