Question

Rate of photosynthesis is maximum in
A. Orange light
B. Yellow light
C. Blue light
D. Green light

Answer 1

Hint: This waveband is within the visible spectrum, with a short wavelength and has relatively high energy. It has pronounced effects on plant growth and flowering. It has wavelengths between 400 and 500 nm.

Complete Answer:
Plants are able to make their own food by using the energy from the sun. This process is known as photosynthesis. During this process, carbon dioxide from the atmosphere is taken in by leaves through stomata and used for making carbohydrates, mainly glucose and starch.

Photosynthesis begins when the light strikes the Photosystem I pigments and stimulates their electrons. Energy passes quickly from molecule to molecule until it approaches a special chlorophyll molecule called P700, so called because it absorbs light in the red spectrum at a wavelength range of 700 nanometres.

The growth of different plant parts is associated with different colours. Blue light is associated with the growth of a plant's leaves and while red light with blue is associated with the growth of flowers in plants. Some red and blue wavelengths of light are considered to be the most effective in the rate of photosynthesis, as they have the necessary amount of energy to stimulate or energise the chlorophyll electrons and raise them from their orbits to a higher energy level.

Green light is not absorbed by the photosynthetic pigments; therefore, green wavelengths are reflected. This is why plants appear green.

Thus, the correct answer is option C i.e., blue light.

Note: The blue end of the visible light spectrum with short-wavelength, high-energy light rays are more easily dispersed than other visible light rays when they strike atmospheric air and water molecules. The greater degree of scattering of these rays makes the cloudless sky appear blue.