The mixture of a pure liquid and a solution in a along vertical column (i.e., horizontal dimensions `lt lt` vertical dimensions) produces diffusion of solute particles and hence a refractive index gradient along the vertical dimension. A ray of light entering the column at right angles to the vertical is deviated from its original path. Find the deviation in travelling a horizontal distance `d lt lt h`, the height of the column.

Explanation

To solve the problem of finding the deviation of a ray of light traveling through a vertical column with a refractive index gradient, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a vertical column filled with a mixture of a pure liquid and a solution. The horizontal dimensions are much smaller than the vertical dimensions, leading to a refractive index gradient along the vertical direction.
- A ray of light enters the column at a right angle to the vertical.

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