Question

How does the visible light spectrum relate to photosynthesis?

Answer 1

Hint: Photosynthesis is the process of manufacture of food by green plants, algae and some bacteria. Photosynthesis is the biological process that derives and harvest solar energy to synthesize carbon compounds from carbon dioxide and water with the generation of oxygen.

Complete answer:
Light is the visible part of electromagnetic radiations. Light exhibits characteristics of both a particle and a wave. Electromagnetic radiations are a form of energy that consists of tiny particles which travel in the form of waves. These particles of light are known as photons and each photon contains an amount of energy called quantum.

Depending upon the wavelength, the electromagnetic spectrum consists of 8 types of radiations: cosmic rays, gamma rays, X-rays, ultra-violet radiations, light spectrum, infra-red rays, electric rays and radio waves.
Visible light consists of radiations that have a wavelength between 390-760 nm. It can be resolved into light of different colours:
- Violet (390-430 nm)
- Indigo (430-470 nm)
- Blue (470-500 nm)
- Green (500-580 nm)
- Yellow (580-600 nm)
- Orange (600-660 nm)
- Red (660-760 nm).

Red light above 700 nm is called far-red. Radiations that are shorter than violet light are called ultra-violet rays. Similarly, radiations longer than those of red are called infra-red. The visible part of the light spectrum is used in photosynthesis that has a wavelength between 400-700 nm. It is called photosynthetically active radiation (PAR). Action spectrum is the graphical representation of the photosynthesis rate at different wavelengths of light. It shows maximum photosynthesis occurs in blue-violet and red parts of the light.

Note: Absorption spectrum is the graphical representation of the amount of light of different wavelengths absorbed by a pigment. It shows that chlorophylls a and b absorb maximum light in the blue-violet and red wavelengths.