Question

Maximum absorption of light by chlorophyll a occurs in which regions of the absorption spectrum (a) Blue (b) Red (c) Green (d) Yellow
a. a and b only
b. b and c only
c. a and d only
d. b and c only

Answer 1

Hint: The role of pigments is to convert the absorbed solar energy into chemical energy. Chlorophyll is a green coloured pigment mainly responsible for giving plants their green colour and absorption of sunlight during the process of photosynthesis. Chlorophyll mainly reflects green and yellow light that is why leaves appear green in colour.

Complete answer:
The light is absorbed through the agency of certain molecules called pigments. There are mainly three types of pigments:- chlorophylls, carotenoids and phycobilins. The chlorophylls are the main pigments while the other two (carotenoids and phycobilins) are accessory pigments. All types of photosynthetic pigments are found in plastids.

The green pigment chlorophylls are the main pigments used in the process of photosynthesis. They mainly absorb red and blue-violet light and reflect most of the blue-green, green and yellow light.

There are seven types of chlorophylls:- chlorophyll a, chlorophyll b, chlorophyll c, chlorophyll d, chlorophyll d, chlorophyll e, bacterio-chlorophyll and bacterioviridin. All these seven chlorophylls are slightly different from each other in absorption spectra. Among all, chlorophyll a is the primary pigment involved in photosynthesis. Light energy absorbed by all other chlorophylls is ultimately transferred to chlorophyll a.

White light is composed of different wavelengths. When it passes through the glass prism, it splits into seven colours i.e., violet, indigo, blue, green, orange and red. This band of seven colours forms the visible spectrum.

Only a small portion of the visible spectrum is utilized for photosynthesis. Maximum absorption of light by chlorophyll a occurs mainly in the blue (470 to 500nm) and red (500 to 580nm) region of the absorption spectrum.

Hence, the correct answer is option (A).

Note: Chlorophyll a, the green pigment of leaves, absorbs mainly the blue and red wavelengths of light of visible spectrum. It mainly reflects the green and yellow wavelengths of the visible spectrum.