The discovery of the eye

Ibn al-Haytham Ibn al-Haytham, an Arab scientist and mathematician, discovered how we see in the 10-11th Century (Islamic Golden Age). During the time he was kept under house arrest, he saw a light shining on the wall. When he observed it carefully it was an image of the buildings outside his room but the image was inverted. This beam of light was projected into his room through a crevice in the wall opposite. Using his hand, he blocked the hole and the image disappeared; he then moved his hand and the image appeared again. This helped him to understand that light bounces off objects and he realised that the eye must do a similar thing. Ibn al-Haytham built a small box with a sheet of paper as one of the sides. On the opposite side of the paper was a small hole. He then placed three lit candles in front of the hole. He observed an inverted image of the three candles. He deduced that the light from the candles bounced off it and then went through the hole, resulting in the image. The box Ibn al- Haytham created was later known as a camera obscurer and helped to create the cameras we all use today. Ibn al-Haytham also discovered that light travels in straight lines.

His work was later developed by other scientists including Kepler in 1604. Fox Talbot used this knowledge to create a camera in 1823.

What are the Components of the Eye?

The eye is composed of seven main parts. The cornea is a layer of transparent skin that covers the front of the eye. It is like a thin sheet of glass and it has no blood vessels in it. The sclera is the tough skin which covers the outside of the eyelid. Most people call it the ‘white bit’ in the eye. The iris is the coloured part in your eye which controls the amount of light allowed into the eye. The pupil is a deep black hole in the centre of our eye that allows light to enter. The eye lens is the part of the eye that focuses light on the retina. The retina uses cones and rods to interpret a picture to send to the brain. The optic nerve sends messages from the eye to the brain.

How Do We See? The images we see are squeezed through the optic nerve and then the image is flipped upside down and travels to the brain. The brain then flips the image the correct way to interpret what the image is.

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