Problem 73 - Objective Biology for NEET

Question

Eye lens of a man is (a) Biconcave (b) Biconvex (c) Concave (d) Convex

Step-by-Step Solution

Answer

The lens of a human eye is (b) Biconvex

Step 1: Understand the structure of the human eye

The human eye is a complex organ with various parts, each having a specific function. The lens of the eye is especially important as it focuses light onto the retina at the back of the eye, enabling us to see clearly. The shape of the lens is crucial to its function.

Step 2: Identify the shape of the lens

In humans, the natural lens is a biconvex or convex-concave lens. This is because both faces of the lens are outward curved or convex, which helps in refracting the light and focus it onto the retina.

Step 3: Compare options with the answer

On comparing the shape of eye lens with the provided options, it's clear that (b) Biconvex is the correct choice. A biconvex shape means it is curved outwards on both sides which is the shape of the human eye's lens.

Key Concepts

Eye Lens Function

The eye lens is a crucial part of our visual system. It plays a significant role in helping us see clearly by focusing light onto the retina. The lens is flexible, allowing it to change shape, which is essential for focusing on objects at different distances. This focusing process is known as "accommodation." The ability of the lens to change shape ensures that light is properly refracted; this means bending the light to focus accurately on the retina.

Key functions of the eye lens include:

• Accommodation: Adjusting its shape to focus on near or distant objects.
• Refraction: Bending light to ensure it lands correctly on the retina.
• Transparency: Remaining clear to allow light to pass through without obstruction.

Any changes in the lens’s clarity or flexibility can affect vision, highlighting its critical role in sight.

Eye Anatomy

The human eye is a complex structure, designed to capture and process light to create images. Each part of the eye has a specific function that contributes to sight. When light enters the eye, it passes through several layers.

The key parts of the eye include:

• Cornea: The eye's outer layer, which acts as a protective barrier and begins focusing light.
• Iris: The colored part, which controls the size of the pupil and thus the amount of light entering the eye.
• Pupil: The opening in the iris, through which light enters deeper into the eye.
• Lens: Changes shape to focus light precisely onto the retina.
• Retina: Contains cells that detect light and convert it into electrical signals.

All these components work in harmony, allowing us to perceive a clear image. The lens plays a pivotal role by adjusting its focus based on light levels and distance of objects.

Biconvex Lens

A biconvex lens is curved outward on both sides. This shape is essential for its role in focusing light effectively. In the human eye, the lens is naturally biconvex, as this shape is optimal for gathering and directing light onto the retina.

The biconvex shape provides several advantages:

• Enhanced Focus: The outward curves allow the lens to bend light more accurately, helping in forming a sharper image.
• Magnification: Because light is bent while passing through a biconvex lens, it can enlarge images, aiding close-up vision.
• Efficiency: As light converges to a focal point, biconvex lenses efficiently bring objects into focus.

Such a structure is not only vital for visual clarity but also in correcting refractive errors, when complemented with corrective lenses for conditions like hyperopia (farsightedness).