"Eyes and Optical Instruments" Light and Eyes PPT Courseware 2

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"Eyes and Optical Instruments" Light and Eyes PPT Courseware 2

long sighted

Hyperopia is when the lens is too flat, and objects are refracted by the lens and appear behind the retina.

Correction: Use a convex lens to first focus the light, and then focus it on the retina through the lens.

Myopia

Myopia occurs when the lens is too convex, causing light to focus in front of the retina.

Correction: Use a concave lens to first diverge the light, and then converge it on the retina through the lens.

Auto zoom bionics

The eye is more like a magical automatic zoom camera. By changing the curvature of the lens, the focal length is changed so that the image can be formed on the retina.

Studying cameras can help us understand how the eyes form images; conversely, further research on the eyes has promoted the continuous development of cameras, especially the emergence of zoom cameras, which is an important example of bionics.

Activity 1: How does it feel to look at objects without my myopia glasses?

Activity 2: Imitate old people reading newspapers. why?

Prescription of glasses

1. The power of glasses is 100 times the reciprocal of the focal length of the lens.

2. The power of convex lenses (lenses for farsightedness) is positive, and the power of concave lenses (lenses for nearsightedness) is negative.

Example 1: Xiao Ming’s glasses are - 400 degrees, his eyes are ________, the focal length of the lens is: ____m, it is __ (convex lens or concave lens)

Example 2: Xiao Ming’s and grandpa’s glasses are placed together. Although grandpa’s glasses are reading glasses and Xiao Ming’s glasses are myopia glasses, the appearance of the two glasses is exactly the same. Please help Xiao Ming use the three simplest methods to distinguish between the two glasses. Glasses.

Answer: ⑴ Feel the shape: The one with a thick middle and thin edges is a far-sighted lens, and the one with a thin middle and thick edges is a myopia lens.

⑵ Look at the image: When you put it on a newspaper, the one that shrinks the virtual image is a myopia lens, and the one that enlarges the virtual image is a far-sighted lens.

⑶Look at the effect on light: those that converge light are far-sighted glasses, and those that diverge light are myopia glasses.

The principle of camera

1. The lens of the camera is equivalent to a convex lens, and the film is equivalent to the screen.

2. Characteristics of camera imaging: inverted, reduced real image

When taking pictures with a camera, if you want the image on the photo to be larger, you should...

Move the camera closer to the object (reduce the object distance),

Extend the camera lens forward (increase the image distance)

After taking a close-up, how should I move the camera before taking a full-body photo?

Move the camera further away from the object (increase the object distance),

Move the camera lens back (reduce the image distance)

Synchronous feedback

1. When a photographer uses a camera to take graduation photos of classmates, the images of the classmates on the camera film ( )

A. Upright and reduced virtual image B. Inverted and reduced virtual image

C. Upright reduced real image D. Inverted reduced real image

2. When a classmate takes photos with a camera, he wants to make the image on the film larger. He should ( )

A. Keep the camera farther away from the person and adjust the lens back.

B. Keep the camera farther away from the person and move the lens forward.

C. Get the camera closer to the person and adjust the lens back

D. Get the camera closer to the person and move the lens forward

Projector use

1. What is the role of a plane mirror here?

Change the propagation path of light so that the image of the projection film appears on the screen in front of the projector

2. How should we display the slideshow if we want to see it standing upright on the screen?

The slideshow needs to be played backwards

Practice in class

1. Which of the following is not an application of lenses in daily life:

A.Camera B.Magnifying glass C.Projector D.Periscope

2. The objects that can be enlarged into real images through the following optical devices are:

A.Camera B.Projector C.Magnifying glass D.Plane mirror

3. The "ginseng wine" currently sold on the market contains a ginseng soaked in a wine bottle. The ginseng you see should be:

A. The real thing of ginseng B. The same size image

C. Enlarged virtual image D. Reduced real image

practise

1 Observe an object through two lenses:

(1) Use a concave lens as the eyepiece and a convex lens with a larger focal length as the objective lens. Adjust the distance between the two and observe distant objects. What you see looks like _______________.

(2) Use a convex lens with a smaller focal length as the eyepiece and a convex lens with a larger focal length as the objective lens. Adjust the distance between the two and observe distant objects. What you see looks like ______________.

(3) Use a convex lens with a larger focal length as the eyepiece and a convex lens with a smaller focal length as the objective lens. Adjust the distance between the two and observe distant objects. What you see looks like _____________.

(4) Generally, the eyepieces and objective lenses of astronomical telescopes use _____ mirrors, and the _____ mirror has a larger focal length.

(5) The eyepieces and objective lenses of a microscope are both _____ mirrors, and the _____ mirror has a larger focal length.

2. After-class practice

Homemade water drop microscope

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Update Time: 2024-11-20

This template belongs to Physics courseware Guangdong and Shanghai version of eighth grade physics volume one industry PPT template

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