In human vision, through which structures of the eye does light pass in the correct order before forming an image on the retina?

Introduction / Context:
The human eye works like a camera, focusing light onto a light sensitive surface. To understand common vision problems and their corrections, it is important to know the path that light takes through different parts of the eye. Questions about the order of structures that light passes through help students build a clear mental picture of how the eye forms images on the retina.

Given Data / Assumptions:
- The structures mentioned are cornea, pupil, lens, and retina.
- The cornea is the transparent front part of the eye.
- The pupil is the opening in the iris through which light enters.
- The lens lies behind the pupil and focuses light.
- The retina is the light sensitive layer at the back of the eye.
- We assume normal forward direction of light entering the eye from the outside world.

Concept / Approach:
When light from an object in front of us enters the eye, it first passes through the cornea. The cornea helps to bend and focus the incoming rays. The light then passes through the aqueous humour and reaches the pupil, the dark circular opening in the centre of the coloured iris. The pupil controls how much light enters the eye. Behind the pupil is the crystalline lens, which further focuses the light by changing its shape slightly. Finally, the focused light reaches the retina, the inner lining at the back of the eye, where photoreceptor cells convert light into nerve signals. Thus, the correct sequence is cornea → pupil → lens → retina.

Step-by-Step Solution:
Step 1: Identify the structure that first meets light from outside the eye: the transparent cornea at the front. Step 2: After passing through the cornea, light travels through the aqueous humour and reaches the opening in the iris, the pupil. Step 3: Behind the pupil sits the lens, which adjusts focus by changing shape. Step 4: The lens focuses the light onto the retina, the light sensitive layer lining the back of the eye. Step 5: Combine these steps to confirm the order: cornea, pupil, lens, retina.

Verification / Alternative check:
Diagrams of the human eye in biology textbooks almost always label the path of light with arrows showing the sequence: cornea at the front → pupil → lens → retina at the back. Explanations of refractive errors like myopia and hyperopia describe how the lens focuses light either in front of or behind the retina instead of directly on it, reinforcing the idea that the retina is the final destination of light in the eye. None of these diagrams place the retina before the lens or the pupil, confirming that the sequence in option A is correct.

Why Other Options Are Wrong:
- Cornea, retina, lens, and then pupil reverses the true positions of the retina and pupil and does not match the actual anatomy.
- Retina, lens, pupil, and then cornea lists the structures from inside to outside and in the wrong order for incoming light.
- None of the above is incorrect, because option A does indeed show the correct sequence.

Common Pitfalls:
Some learners may confuse the order of structures because they focus more on their names than their positions. Others may mistakenly think that the retina comes earlier because it is associated with image formation. To avoid confusion, it helps to visualise the eye from the side and imagine light entering from the air: it must first pass through the transparent front (cornea), then go inside through the pupil, be focused by the lens, and finally reach the retina at the back. Remembering this pathway makes it easy to answer questions about the order correctly.

Final Answer:
Light passes through the eye structures in this order: Cornea, pupil, lens, and then retina at the back of the eye.