(a) A mobile phone lies along the principal axis of a concave mirror. Show, with the help of a suitable diagram, the formation of its image. Explain why magnification is not uniform.
(b) Suppose the lower half of the concave mirror's reflecting surface is covered with an opaque material. What effect this will have on the image of the object? Explain.

Explanation

### Step-by-Step Solution

#### Part (a): Formation of Image by a Concave Mirror

1. **Understanding the Setup**:
- A mobile phone is placed along the principal axis of a concave mirror.
- The principal axis is the straight line that passes through the center of the mirror and its focus.

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