Correct option is A
Explanation:
Statement A: Correct
- Absorption of light (photon) excites a pigment molecule.
- When chlorophyll absorbs a photon, an electron moves from the ground state to an excited state.
- The energy difference between these states is equal to the absorbed photon's energy.
- This is the fundamental process in photosynthesis.
Statement B: Correct
- After excitation, electrons return to the lowest excited state before releasing energy.
- This process is known as internal conversion or relaxation.
- The energy lost is dissipated as heat, making it a non-radiative transition.
- It ensures that photochemical reactions occur from the lowest excited state.
Statement C: Correct
- When chlorophyll molecules return to the ground state from their lowest excited state, they emit energy as fluorescence (a lower-energy photon).
- Chlorophyll fluorescence occurs at a longer wavelength (red region) due to energy loss as heat.
- This is important in measuring photosynthetic efficiency in plants.
Statement D: Incorrect
- Blue light has more energy than red light because energy is inversely proportional to wavelength (E = hν = hc/λ).
- Chlorophyll absorbs blue light (shorter wavelength) at a higher energy level than red light.
- Thus, blue light excites electrons to a higher state than red light, making this statement incorrect.
