When a ray of light travelling in air enters obliquely into a glass slab, it is observed that the light ray emerges parallel to the incident ray but it is shifted sideways slightly. Draw a labelled ray diagram to illustrate it.

Explanation

### Step-by-Step Solution:

1. **Draw the Glass Slab**: Start by drawing a rectangular shape to represent the glass slab. This will be the medium through which the light ray will pass.

2. **Draw the Normal Line**: At the point where the light ray will enter the glass slab, draw a vertical dashed line. This line is called the normal line and it is perpendicular to the surface of the glass slab.

3. **Draw the Incident Ray**: From the left side of the diagram, draw a slanted line approaching the glass slab. This line represents the incident ray of light. Label this line as "Incident Ray".

...