Why in a photocell the cathode is coated with alkali metals ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Photocell**:
A photocell consists of two plates: a cathode and an anode. When light (or other radiation) hits the cathode, it can cause electrons to be emitted, creating a flow of current.

2. **Role of the Cathode**:
The cathode is the electrode from which electrons are emitted when it is illuminated by radiation. The material used for the cathode is crucial for the efficiency of the photocell.

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