The Human Eye LG: I can describe the parts and function of the human eye and describe the types of images we observe and the reasons for common vision problems

Recall: Images in Converging Lenses Converging images can produce 2 types of images: Large upright image produced when object is in front of the focal point Example: Magnifying glass Small, inverted image produced when object is further than the focal point Example: Human eye

The Human Eye: Parts and Function

The Human Eye The human eye sees through a converging lens. The objects we can see clearly are further than the focal point of our eye This means our eye sees a smaller, inverted image Light rays converge on the retina (back of the eye, where rod and cone cells are located) Interesting fact: There are no rod or cone cells at the point where the optic nerve connects to the eye which produces a “blind spot”

Check your Blind Spot! Hold the paper about 30 cm away, so the circle is on the left Cover your left eye and slowly bring the paper toward your face What happens to the star? At what distance does this occur? Explanation: Each eye has a blind spot, but our brains “merge” the images from each eye into one picture, so we don’t notice

Vision Problems When light rays do not meet at the retina, a clear image cannot be seen Myopia (nearsightedness) – light rays meet in front of retina Hyperopia (farsightedness) – light rays meet behind retina What kind of lens could you used to correct each problem?

Vision Correction Lenses may be used to adjust the point where light rays converge on the retina Concave lenses are used to correct nearsightedness Convex lenses are used to correct farsightedness