Optics_2_0212_handout

# Optics_2_0212_handout - Optics 2 The Human Eye Model In...

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PHYS 0212 Optics 2 1 Optics 2 This experiment has five parts: 3. Double Slit Diffraction 2. Single Slit Diffraction 4. Diffraction Grating (Multiple Slit Diffraction) 5. Holography 1. The Human Eye PHYS 0212 Optics 2 2 The Human Eye Model In your eye, the image distance is the distance between your lens and your retina. The object distance is the distance between your lens and whatever you are looking at. Since the image distance is fixed the focal length of the lens must be able to change in order to keep objects in focus that are at varying distances in front of the eye. The thickness of a lens effects its focal length. The thicker the lens the shorter the focal length. The thickness of the lens in the human eye is controlled with muscles that squeeze or stretch it. This process is called accommodation . PHYS 0212 Optics 2 3 The lens of the eye can only be squeezed so much, so once an object gets too close to the eye it can no longer be accommodated and so it will no longer be in focus. This is called the near point of the eye - The minimum distance from the eye at which an object is in focus. f f Distant Object Near Object f PHYS 0212 Optics 2 4 Syringe Lens Holder Length Adjustment Fluid Filled Lens Cornea Retina Normal Eye The eye model you will use has a fluid-filled lens with an adjustable volume to simulate the process of accommodation. The lens is filled with distilled water and the volume is adjusted with a syringe. As the volume of the lens increases the focal length decreases. 1. Find the near point of the eye model and compare to the near point of your own eye. 2. Make a plot of the syringe volume versus object distance.

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PHYS 0212 Optics 2 5 Syringe Lens Holder Length Adjustment Fluid Filled Lens Cornea Retina Myopic Eye The Myopic (Nearsighted) Eye In a myopic eye the image forms in front of the retina. We can simulate this with the model by increasing the distance between the lens and the retina. 1. Focus an object with the normal eye. 2. Adjust the position of the retina so it is farther away. 3. Show that this change causes nearsightedness. 4. Use a diverging lens to correct for the myopia. PHYS 0212 Optics 2 6 Syringe Lens Holder Length Adjustment Fluid Filled Lens Cornea Retina Hyperopic Eye The Hyperopic (Farsighted) Eye In a hyperopic eye the image forms behind the retina. We can simulate this with the model by decreasing the distance between the lens and the retina.
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Optics_2_0212_handout - Optics 2 The Human Eye Model In...

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