# Unit 3.1Medical Physics. TITLE: The eye Objectives (We are learning that): What are the parts of the eye and what are their functions? What is the power.

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Unit 3.1Medical Physics

TITLE: The eye Objectives (We are learning that): What are the parts of the eye and what are their functions? What is the power of a lens? What is long and short sightedness? How can we correct it? KEY WORDS: Iris Cornea Pupil Ciliary muscles Retina Focal point Focal length Fovea Outcomes: You should be able to... Identify the parts of the eye and their basic functions. (C) Draw a ray diagram for a distant and a near object to the eye. (B) Describe the conditions of long and short sightedness. (B) Calculate lens power or focal length. (A/A*) Explain why manufacturers can make powerful, yet thin lenses for glasses. (A*)

Starter Activity Create a P3 keyword glossary for the following key terms. You can use images/diagrams etc: Converging, convex, concave, diverging, refractive index, critical angle, focal length, blind spot, real image, virtual image, endoscope, charge coupled device, dioptive, radiograph, CT scanner

Label the parts of the eye above: (grade C) Find the functions of the following parts of the eye: CORNEA, LENS, CILIARY MUSCLE, CILIARY LIGAMENT, IRIS, PUPIL, RETINA. Write a short description of their functions. Use the web or a textbook. (GCSE Grade B) TASK 1

Copy and complete the following sentence : (grade C) “To see an object that is _______ to you, your eye’s lens must change so it becomes ______ and _______. This is because it needs to ________ light rays more towards the ________. TASK 2

Read the information concerning long and short sightedness on the next two slides. Answer the following questions in your book. 1. Using his left eye, a student needs to sit at the front of the class in order to see the board clearly. a) What sight problem does he suffer from in his left eye? b) What type of lens can he use to correct this problem? 2. A teacher suffers from long sightedness. What three physical things has made them long sighted? For further explanation, go to this web address: http://www.freezeray.com/flashFiles/eyeDefects.htm http://www.freezeray.com/flashFiles/eyeDefects.htm TASK 3

Extension Task: How can we make powerful lenses thin? Contact lenses have been around for over 100 years. In the late 19 th century small pieces of glass were made to put onto people’s eyes. They were made to have a small cavity that was filled with water, oil or animal fat to refract light rays. In the 1930s plastics were engineered to replace the glass but these were still very large, thick, heavy, uncomfortable and above all very expensive. In the next 50 years lenses became smaller but still needed to be thick to refract light rays enough. In 1998 silicone based plastic lenses were first made that could be thin enough to be more comfortable and powerful. These substances have a large refractive index. This means that they have the power to refract light well despite being thinner.

TITLE: The eye Objectives (We are learning that): What are the parts of the eye and what are their functions? What is the power of a lens? What is long and short sightedness? How can we correct it? KEY WORDS: Iris Cornea Pupil Ciliary muscles Retina Focal point Focal length Fovea Outcomes: You should be able to... Identify the parts of the eye and their basic functions. (C) Draw a ray diagram for a distant and a near object to the eye. (B) Describe the conditions of long and short sightedness. (B) Calculate lens power or focal length. (A/A*) Explain why manufacturers can make powerful, yet thin lenses for glasses. (A*)

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