In a prism, light undergoes bending towards the normal at one surface and away from the normal at the other. In a glass slab, the bending occurs only once, either towards or away from the normal depending on the direction ...

At the second surface AC, the light ray exits from glass to air, bending away from the normal. This is in contrast to the first surface where the bending was towards the normal.

Light is refracted through a transparent prism by passing through its three rectangular lateral surfaces. The triangular glass prism has two triangular bases and three rectangular lateral surfaces that are inclined to each other.

In a glass slab with parallel refracting surfaces, the emergent ray is parallel to the incident ray, but it is slightly displaced laterally.

Modern alternatives for correcting refractive defects include contact lenses and surgical interventions. These options provide additional choices beyond traditional corrective eye-glasses.

Bi-focal lenses are designed with the upper portion as a concave lens for distant vision and the lower part as a convex lens for near vision. This design allows individuals to see clearly at both distances.

Individuals experiencing both myopia and hypermetropia often require bi-focal lenses, which consist of both concave and convex lenses. The upper part facilitates distant vision, while the lower part assists near vision.

Presbyopia arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens.

Presbyopia is a defect where the near point gradually recedes as the power of accommodation decreases with age. People find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses.