Glass Slab with Variable Refractive Index

Q. When light ray travels from optically denser to optically rarer medium the velocity of light increases and thus wavelength decrases to maintain the constant frequency. But what is this frequency of light and why does it need to be constant? What will happen if it is not maintained?(being hypothetical)

Q.

We have a glass slab whose refractive index varies with distance 'x'. The emergent ray will be parallel to the incident ray.

1. True

2. False

Q. Refraction in a parallel glass slab, implies that the incident ray is always parallel to the emergent ray.

1. True
2. False

Q. Choose the correct statement for a rectangular glass slab?

1. The emergent ray is parallel to the incident ray.
2. The emergent ray is inclined to the incident ray.
3. The emergent ray coincides with the incident ray.
4. The emergent ray is perpendicular to the incident ray

Q. Choose the correct statement for a rectangular glass slab?

1. The emergent ray is parallel to the incident ray.
2. The emergent ray is inclined to the incident ray.
3. The emergent ray coincides with the incident ray.
4. The emergent ray is perpendicular to the incident ray