State Einstein’s photoelectric equation and explain the terms involved.

Explanation

### Step-by-Step Solution:

**Step 1: State Einstein's Photoelectric Equation**
Einstein's photoelectric equation is given by:
\[ KE_{\text{max}} = hf - \phi \]

**Step 2: Define the Terms Involved**
1. **\( KE_{\text{max}} \)**: This represents the maximum kinetic energy of the ejected electron. It indicates the energy that the electron possesses after being emitted from the surface of a material due to the photoelectric effect.
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