A light ray is incident on a plane mirror at an angle of `30^(@)` with horizontal. At what angle with horizontal must a plane mirror be placed in its path so that it becomes vertically upwards after reflection?

Explanation

To solve the problem, we need to determine the angle at which a plane mirror must be placed so that a light ray, initially incident at an angle of 30 degrees with the horizontal, reflects vertically upwards.

### Step-by-Step Solution:

1. **Understand the Geometry**:
- Draw a diagram with a horizontal line representing the ground.
- Draw a light ray incident on a mirror at an angle of 30 degrees with the horizontal.
- Let the angle between the mirror and the horizontal be denoted as θ.
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