Question

Assertion: Action spectrum of photosynthesis compares well with the absorption spectrum.

Reason: Chlorophyll a is the only pigment which can absorb and convert light energy into chemical energy.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is: (b)

Explanation:

An absorption spectrum is a measure of the extent to which a given substance absorbs the light of different colours or wavelengths. An action spectrum is the measure of the efficiency of a process induced by light of different wavelengths but of the same intensity or in other words it is the measure of relative rates of photosynthesis at different wavelengths of light. It is actually a plot of the extent of a response (such as photosynthesis) against different wavelengths of light. A comparison of an action spectrum with the absorption spectrum of a pigment indicates whether or not the pigment is involved in the response. For example, the absorption spectrum of chlorophyll a is very similar to the action spectrum of photosynthesis in most plant tissues. Although, light energy is absorbed by chlorophyll as well as by other accessory pigments, only chlorophyll a participates in conversion of light energy to chemical energy.