Question

Which light range is least effective in photosynthesis?
A) Blue
B) Green
C) Red
D) Violet

Answer 1

Hint: Photosystems present in the thylakoids absorb specific wavelengths of light. Red light is highly efficient light for the process of photosynthesis. The best wavelength ranges between 680 and 700 nm. Wavelength of green light ranges from 495-570 nm.

Complete answer:
Photosynthesis occurs in the presence of sunlight. Chloroplasts present in the leaves absorb a certain wavelength of light. Two types of photosystems are present in the thylakoids of the chloroplast. Photosystem I absorb the light of wavelength 700 nm while the photosystem II absorbs best at 680 nm. Blue light ranges from 425 to 450 nm while the red light ranges from 600 to 700 nm. The best wavelength for the visible light for photosynthesis lies between blue and red light. Blue light carries more energy than the red light. Leaves absorb most of the red and blue light but most of the green light. The violet light ranges from 380 – 450 nm. Other wavelengths such as yellow and orange wavelengths range from 570-590 and 590-620 respectively.
In the visible spectrum green light is the least efficiently used color. The wavelength of green light ranges from 495 – 570 nm. The frequency of green light is 5.45 ($10^4$ Hz).
From the above information we have found that green light range is least effective in photosynthesis.

So, the correct answer is option B.

Note: Red light has a wavelength of about 700 billionths of a meter which is very small. Longer wavelengths have less energy. Wavelength is inversely proportional to the frequency. Light behaves as a wave, it can reflect, refract and diffract. Photons are present in the light. Energy of photons depends on its frequency. Each photon has its specific wavelength.