The human eye!

Many of us take our vision for granted, but have you ever wondered how this fascinating organ actually works?

Light from the sun, or an artificial light, travels in a straight line, bounces off objects and into our eyes through the pupil. Depending on the amount of light, the iris changes the size of the pupil to let more or less light in. This is to prevent damage to the eyes, by stopping too much light entering the eye when it is bright, and maximising the amount of light entering the eye when it’s dark.

The light then passes though the lens. The lens focuses the light onto the back surface of the eye, the retina. Depending on how far away the object is, our lens needs to change shape to keep the light focussed on the retina.

 

How the lens focusses light.

A fatter lens bends light more than a flatter lens. The human eye changes the shape of the lens as we look at far or near objects to keep them in focus. This is called accommodation. When we look at a far object, the light does not need to bend a lot to converge on the retina, so the suspensory ligaments pull on the lens to make it flat. When we look at a near object, the light has to bend more to converge on the retina, so the suspensory ligaments pull less, allowing the lens to spring back into a fatter shape.

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