PASCO OS-8477A - Manuals

® M o d e l N o . O S - 8 4 7 7 A M a i n t e n a n c e a n d S t o r a g e 3 Demonstration Without Water The eye model can be used with or without water. With no water, and no changeable lenses in place (using only the corneal lens), the eye model focuses at optical infinity. Set the eye model to l...

® H u m a n E y e M o d e l S p e c i f i c a t i o n s 4 Specifications Model Eye Movable Lenses Focal Lengths (In Air) Index of Refraction (Polycarbonate Plastic) Plano-convex Corneal Lens Index of Refraction (Glass) Dimensions 15 cm × 17 cm × 10 cm Water Capacity 1 liter Retina Diameter 7 cm Mate...

® M o d e l N o . O S - 8 4 7 7 A A d j u s t a b l e F o c u s L e n s 5 Adjustable Focus Lens The Adjustable Focus Lens includes two lenses, a length of plastic tubing, and a 10 mL syringe. Each lens consists of a plastic housing and two flexible membranes. The syringe is used to fill the lens wit...

® H u m a n E y e M o d e l A d j u s t a b l e F o c u s L e n s 6 4. Do not force the liquid from the syringe into the lens holder. Instead, slowly pull the piston out so that air from inside the lens holder bubbles up through the liquid in the cylinder. The liquid should begin moving drop-by-drop...

® 7 H u m a n E y e M o d e l Background How Lenses Form Images Light rays are bent, or refracted, when they cross an interface between two materials that have different indices of refraction. The index of refraction of a material is the ratio of the speed of light in a vacuum to the speed of light ...

® H u m a n E y e M o d e l B a c k g r o u n d 8 Images and Image Distance When an object is placed in front of a lens, the light from the object passing through the lens forms an image. There are two types of images: real and virtual. A real image is formed by converging rays at the point where th...

® M o d e l N o . O S - 8 4 7 7 A B a c k g r o u n d 9 Magnification The size of an image can be different from the size of the object. The relative magni- fication , , of the image is defined by: (eq. 2) If is greater than 1, the image is larger than the object; if is less than 1, the image is sma...

® H u m a n E y e M o d e l B a c k g r o u n d 10 near the center of the retina, contains only cones and is responsible for the most acute vision. Signals from the rods and cones are carried by nerve fibers to the optic nerve , which leads to the brain. The optic nerve connects to the back of the e...

® M o d e l N o . O S - 8 4 7 7 A B a c k g r o u n d 11 A form of hypermetropia called presbyopia (old-sightedness) is not caused by the shape of the eye, but by a change in the crystalline lens: over time, the lens becomes more rigid, making it less able to accommodate to short object distances. A...

® H u m a n E y e M o d e l B a c k g r o u n d 12 focal length of the lens. Reading glasses can be thought of as a type of magnifying glass that allow you to hold a book nearer than your eyes’ near point while viewing a more distant image of the book. A microscope is a combination of two or more le...

® 13 H u m a n E y e M o d e l Experiment Setup This table summarizes the equipment needed for the following experiments. With the exception of the eye model itself, the specific model numbers suggested here can be substituted with similar items from PASCO or other manufacturers. See “Equipment and ...

® H u m a n E y e M o d e l E x p e r i m e n t S e t u p 14 Water They eye model requires about one liter of water, but do not fill it yet if you are going to do Experiment 1. When you remove lenses from the model, they will be wet; have an absorbent cloth or paper towel ready to lay them on. Do no...

® 15 H u m a n E y e M o d e l Experiment 1: Optics of the Human Eye In this experiment you will study how images are formed on the retina of the eye. Before you start, draw a diagram of the eye model and identify the parts of the human eye represented by each part of the model. Part 1: Images Forme...

® H u m a n E y e M o d e l E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 16 Part 2: Accommodation In the process of accommodation, muscles in the eye change the shape of the crystal-line lens to change its focal length. Initially, you will model accommodation by vary-ing the focal l...

® M o d e l N o . O S - 8 4 7 7 A E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 17 7. The optics of a two-lens system can be simplified looking at the combined effect of the lenses and the total effective focal length of the system. Measure the image distance ( i ), from the model’s ...

® H u m a n E y e M o d e l E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 18 13. Calculate the total effective focal length of the lens system, as you did in step 7. What value should you use as the object distance for far vision? How do you enter that value into a calculator? (Hint:...

® M o d e l N o . O S - 8 4 7 7 A E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 19 3. Turn the eye model to look at the distant object, and describe the image. Does a far-sighted person have trouble seeing distant objects? Why was it not necessary to change the lens to look far away?...

® H u m a n E y e M o d e l E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 22 glasses, look at the figure both with and without your glasses. Try rotating your glasses in front of your face while looking at the chart through one of the lenses. 2. Set the eye model to normal, near visi...

® H u m a n E y e M o d e l E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 24 Questions 1. In order to repeat the blind-spot exercise in step 1 with your left eye , what do you have to do differently? 2. Try repeating the blind-spot exercise, but look at the image with both eyes. Why ...

® M o d e l N o . O S - 8 4 7 7 A E x p e r i m e n t 1 : O p t i c s o f t h e H u m a n E y e 25 4. Make a copy of this diagram and label it with the object size, image size, object distance, and image distance that you measured in step 1 of the procedure. Show that the two triangles in the diagra...

® 27 H u m a n E y e M o d e l Experiment 2: Telescope In this experiment you will build a telescope and use it to view the light source, both with your own eye and with the model eye. Procedure 1. Place the light source on the optics bench. Align the illuminated object screen with the 0 cm mark. 2....

® H u m a n E y e M o d e l E x p e r i m e n t 2 : T e l e s c o p e 28 formed with the telescope? Measure the width of the image. Draw another sketch of the retina and image. Analysis 1. Divide the retina image size viewed with the telescope by the retina image size without the telescope. This is ...

® M o d e l N o . O S - 8 4 7 7 A E x p e r i m e n t 2 : T e l e s c o p e 29 2. In your model telescope, the positions of the two lenses were chosen to make Image #2 form at about the same location as the object on the light source. If you adjusted the telescope to form the image at infinity, what...

® 31 H u m a n E y e M o d e l Experiment 3: Refraction, a Detailed Study As light travels from an object to the retina, it crosses several surfaces that mark the boundaries between different media. At each surface, light is bent, or refracted. In Experiment 1, the analysis of the eye model was simp...

® H u m a n E y e M o d e l E x p e r i m e n t 3 : R e f r a c t i o n , a D e t a i l e d S t u d y 32 Image Produced by a Single Flat Surface Even though the interface between the glass corneal lens and the water behind it is flat, it still produces an image. The figure below shows light rays ben...

® M o d e l N o . O S - 8 4 7 7 A E x p e r i m e n t 3 : R e f r a c t i o n , a D e t a i l e d S t u d y 33 Procedure 1. Fill the eye model with water and set it for normal, far vision (with the +120 mm lens in the SEPTUM slot). Make the eye model look at a distant object. The image should be in ...

® H u m a n E y e M o d e l E x p e r i m e n t 3 : R e f r a c t i o n , a D e t a i l e d S t u d y 34 9. Where is Image #3? Can you see it? 10. Measure the distance from the crystalline lens to the retina screen. How does dis-tance compare to your result from step 8? Questions 1. Are Image #1 and...

® 35 H u m a n E y e M o d e l Other Suggested Activities Flat Mirror Set the eye model for normal, near vision (with the +62 mm lens in the SEPTUM slot) and focus it on a nearby light source. Note the object distance. Use desk lamp to brightly illuminate the front of the eye (but shade the retina w...

® H u m a n E y e M o d e l O t h e r S u g g e s t e d A c t i v i t i e s 36 Retinoscopy Using the method known as retinoscopy, an ophthalmologist examines the refractive properties of the eye by illumining and area of the retina and observing the image that is formed by light that exits the eye. ...

® 37 H u m a n E y e M o d e l Teachers’ Notes Experiment 1: Optics of the Human Eye Part 1 Students should find that images on the retina are inverted and that the image of an upside-down object looks like a right-side-up mirror image. Part 2 Students should find that a image forms on the retina wh...

® H u m a n E y e M o d e l T e a c h e r s ’ N o t e s 38 The distance from the +120 mm lens to the object is 9 cm. The calculated image dis-tance for this lens is -36 cm. The calculated magnification of the virtual image is +4. Experiment 2: Telescope With the telescope set up as described, f 1 = ...

® M o d e l N o . O S - 8 4 7 7 A T e a c h e r s ’ N o t e s 39 Experiment 3: Refraction, a Detailed Study The distance of the first image from the curved surface of the cor-neal lens is The object distance ( o 2 ) is i 1 minus the thickness of the lens. Also, Image #1 (which becomes Object #2) is ...

® H u m a n E y e M o d e l T e c h n i c a l S u p p o r t 40 Technical Support For assistance with any PASCO product, contact PASCO at: Limited Warranty For a description of the product warranty, see the PASCO catalog. Copyright The PASCO scientific 012-13032A Human Eye Model Instruction Manual is...