"Eye and Glasses" Lens and its Application PPT Teaching Courseware

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"Eye and Glasses" Lens and its Application PPT Teaching Courseware

The first part: sorting out new knowledge

1. The structure and imaging principle of the eyeball

1. Structure of the eyeball and imaging principle

As shown in the picture, the eyeball is like a ________. The lens and the cornea work together to condense the light from the object on the ________ (equivalent to a light screen) to form a __________ of _____. _picture.

2. Eye adjustment method

As shown in Figure 5-4-2, normal eyes can not only look at distant scenery, but also take a closer look at close objects. The reason why a clear image can be formed on the retina even if the object distance changes and the image distance remains unchanged is: the eye changes the shape of ______ through the ciliary body, thereby changing the ______ of the lens, so that the external scenery at different distances and nears can be seen clearly. Can be imaged on the retina through the lens.

2. Causes and correction of myopia and hyperopia

Eyes and Glasses PPT, Part 2: Application Examples

Type 1: Structure of the eyeball and imaging principle

Example 1: Figure 5-4-5(a) shows a schematic diagram of a person observing distant objects. At this time, the lens becomes thinner and the focal length of the eye _____ (optional "get bigger" or "get smaller"), The image just happens to be on the retina. As shown in Figure (b), it is a schematic diagram of a person observing a nearby object. At this time, the lens becomes thicker, the focal length of the eye ________ (optional "gets bigger" or "gets smaller"), and the image is just right on the retina. , this person’s vision _______ (optional “normal” or “abnormal”). The eye is a "convex lens" with a focal length of ________ (optional "constant" or "variable").

[ Analysis A "convex lens" with variable focal length. Because this person can see both distant and near objects as images on his retina, his vision is normal.

Example 2: Compare the structures of the eye and the camera shown in Figure 5-4-6, and fill in the table with components with similar functions between the camera and the eye.

[ Analysis , only when the shutter is opened can light enter.

Type 2: Myopia, hyperopia and their correction

Example 3 2018·Changsha In modern life, smartphones have brought many conveniences to people, but staring at the screen of the mobile phone for a long time can easily lead to vision loss. As shown in Figure 5-4-5, the correct schematic diagram about myopia and its correction is ()

A.A,B B.A,D C.C,B D.C,D

[ Analysis Human eyes have diverged once before, so they wear concave lenses that have a divergent effect on light to correct them. That is, Figure B can correctly represent the correction of myopia. In Figure C, the refracted light rays converge behind the retina, so Figure C shows the imaging situation of the hyperopic eye; in the hyperopic eye, because the focal length of the lens is too large, the image falls behind the retina, in order to make the light converge on the retina in front of the original point of convergence. , it is necessary to make the light converge once before entering the human eye, so it is corrected by wearing a convex lens that has a converging effect on the light, that is, Tuding can accurately represent the correction of hyperopia.

[Method guidance]How to determine myopia and hyperopia

(1) Myopia: ① Parallel light from a distance converges in front of the retina; ② Only close objects can be seen clearly but distant objects cannot be seen clearly.

(2) Hyperopia: ①Light from near places converges behind the retina; ②Only distant objects can be seen clearly, but nearby objects cannot be seen clearly.

Eyes and Glasses PPT, Part 3: Class Feedback

1. When using a camera, the distance from the scene to the lens should be far ______ (optional "greater than" or "less than") the focal length of the lens. Figure 21-1 is a schematic diagram of the eye. The human eye is like a camera. The lens and cornea work together as a _____ lens. The image formed by external objects on the retina is ______ (optional " upright" or "inverted") real image.

2. Figure 21-2 shows the imaging diagram of a normal eye. Regarding normal eyes, which of the following statements is wrong ()

A． When looking at distant objects, the ciliary body relaxes and the lens becomes thinner

B. When looking at nearby objects, the ciliary body tightens and the lens thickens

C. When looking at nearby objects, the ciliary body relaxes and the lens thickens

D. The visual distance of normal human eyes is approximately 25 cm

3． Regarding myopia, which of the following statements is correct ()

A． Myopia can only see nearby objects clearly, but not distant objects.

B. Myopia is caused by the lens being too thick and its refractive power too weak

C. Myopia lenses are convex lenses

D. Myopia causes light rays from far away to converge behind the retina

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For more information about the PPT courseware "Lens and Its Applications in Eyes and Glasses", please click the "Lens and Its Applications ppt Eyes and Glasses ppt" tag.

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Update Time: 2024-11-22

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 1 industry PPT template

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