"Magical Eyes" Colorful Light PPT Courseware 3

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"Magical Eyes" Colorful Light PPT Courseware 3

Two convex lenses with the same diameter have focal lengths of 8cm and 16cm respectively. Which lens deflects light more? What conclusions can you draw from this? If you examine the concavity and convexity of the lens again, what other conclusions can you draw?

Conclusion: The more convex the convex lens, the stronger the refractive power!

How do we see objects?

in conclusion:

1. The objects we see are inverted and reduced real images formed through the lens.

2. The lens is equivalent to a convex lens, and the retina is equivalent to a light screen.

Guess: How do we see distant objects as well as nearby objects?

Normal eye accommodation:

The eye uses the ciliary body to change the shape of the lens:

When the ciliary body is relaxed, the lens is relatively thin, and the light from distant objects just converges on the retina, and the eyeball can see distant objects clearly;

When the ciliary body contracts, the lens becomes thicker and its ability to deflect light becomes larger. Light from nearby objects converges on the retina, and the eyeball can see distant objects clearly.

in conclusion:

The human eye changes the focal length of the convex lens (lens) by changing the shape of the lens, so that both distant objects and near objects can be seen.

Myopia

Some people have difficulty seeing distant objects. They have to put the object closer to their eyes to see clearly.

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.

long sighted

Some people have difficulty seeing close objects. They have to place the objects further away from their eyes to see them clearly.

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.

Prescription of glasses

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

Example 1: Xiao Ming’s glasses are -200 degrees, his eyes are _________, the focal length of the lens is: ____m, it is _ _ (convex lens or concave lens)

2: Xiao Ming’s and grandpa’s glasses are put 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 the two 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.

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What are the rules of imaging by convex lenses?

When u>2f, it becomes an inverted, reduced, real image, and the image and the object are on opposite sides of the lens.

when f

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"Magical Eyes" Colorful Light PPT Courseware Two convex lenses with the same diameter, their focal lengths are 8cm and 16cm respectively. Which lens deflects light more? What conclusions can you draw from this? Then check the concave and convex degree of the lens, you can also get...

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Update Time: 2024-10-14

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