Question

Red drop occurs in wavelength of

• A. 492 nm
• B. 535 nm
• C. 586 nm
• D. 680 nm

Answer 1

The correct option is D 680 nm

An action spectrum of photosynthesis is defined as the rate of photosynthesis plotted against wavelength of light.
Robert Emerson observed that there was a sudden fall in the rate of photosynthesis in the far red region (greater than 680 nm) of the electromagnetic spectrum.
This wavelength of 680 nm, after which the sudden fall in the rate of photosynthesis is observed is called as red drop.