First step of light phase of photosynthesis is :-

Options

A. Excitation of chlorophyll by light
B. Photolysis of water
C. Synthesis of ATP
D. Synthesis of NADPH

Answer

### Step-by-Step Solution:

1. **Understanding Photosynthesis**: Photosynthesis occurs in two main phases: the light phase (light-dependent reactions) and the dark phase (light-independent reactions). The light phase is initiated when light energy is absorbed.

2. **Role of Chlorophyll**: Chlorophyll is the primary pigment involved in photosynthesis. It is located in the chloroplasts of plant cells and is essential for capturing light energy.

3. **Absorption of Light**: When light hits the chlorophyll molecules, they absorb specific wavelengths of light. This absorption of light energy is crucial for the photosynthesis process.

4. **Excitation of Electrons**: The absorbed light energy causes the electrons in the chlorophyll to become excited. This means that the electrons gain energy and move to a higher energy state.

5. **Electron Transfer**: The excited electrons are then transferred to an electron acceptor. This initiates a series of reactions in the electron transport chain, which is essential for the production of ATP and NADPH later in the light phase.

6. **Conclusion**: The first step of the light phase of photosynthesis is the excitation of chlorophyll by light.

### Final Answer:
The first step of the light phase of photosynthesis is **excitation of chlorophyll by light**.

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