Principles of Light Reflection and Human Vision

Reflection of Light and Its Fundamental Laws

The reflection of light is the change of direction a light beam undergoes when striking the surface of bodies.

Types of Reflection

• Specular reflection: This occurs when light reflects off a polished surface, such as a mirror.
• Diffuse reflection: This occurs when the surface is rough and the light is reflected in all directions.

The Two Fundamental Laws of Reflection

The reflection of light on a flat surface follows two fundamental laws:

1. The incident ray, the normal, and the reflected ray are all on the same plane.
2. The angle of incidence equals the angle of reflection.

Electromagnetic Waves and the Nature of Color

Different electromagnetic waves that we perceive as red, yellow, green, blue, indigo, and violet differ only in wavelength; therefore, light itself has no inherent color. Color is interpreted because our brain perceives different frequencies that reach our eyes. Colors are a creation of our perception.

We see plants as green because they absorb light of all frequencies except the one corresponding to green, which is reflected. When light is refracted, waves are separated into different frequencies; we call this dispersion.

Common Vision Defects and Their Causes

Most vision defects occur because the image is not formed correctly on the retina. This can be due to two causes: the eyeball is too long or short, or the lens cannot adjust its curvature to form the image on the retina.

• Myopia: In an eye with this defect, the image is formed in front of the retina. It can be compensated for with divergent lenses.
• Hyperopia: In this case, the image is formed behind the retina. This defect may be compensated for by converging lenses.
• Astigmatism: Images are perceived as distorted because the cornea is deformed. It is corrected with cylindrical lenses.
• Presbyopia: This eye defect is the impossibility of seeing close objects with clarity due to the rigidity of the lens. It is also called farsightedness.

Anatomy of the Eye and Camera Comparison

• The Iris: Regulates the opening of the pupil and, therefore, the amplitude of the light band that hits the retina; it behaves like a diaphragm.
• The Crystalline Lens: A clear lens that can change its shape to converge light rays onto the retina; it serves as the target.
• The Posterior Chamber: Occupied by the vitreous humor, it can be compared to a darkroom.
• The Retina: The inner layer stimulated by light rays; it behaves like a sensitive film.