"Lens" Lens and its applications PPT courseware 5

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"Lens" Lens and its applications PPT courseware 5

Preview test

1. Types of lenses

(1) Convex lens: ___________ lens.

(2) Concave lens: ___________ lens.

2. Main optical axis and optical center

(1) Principal optical axis: a straight line passing through two spherical surfaces___________. Abbreviated as___________.

(2) Optical center: a special point on the main axis of the lens. The propagation direction of any light passing through it is ___________.

3. The effect of lens on light

(1) Convex lenses have a ___________ effect on light, also called ___________.

(2) Concave lenses have a ___________ effect on light, also called ___________.

4. Focus and focal length

(1) Focus: ___________ the light ray from the main optical axis of the convex lens is refracted by the convex lens at a point ___________, which is symbolized by ___________.

(2) Focal length: the distance from ___________ to ___________, represented by the symbol _____

(3) The smaller the focal length of the convex lens. The converging effect of a lens on light___________.

Lens: Lenses are generally made of light-transmitting materials such as glass, and their surfaces are part of a sphere.

See what's the difference between these lenses?

Convex lens: A lens that is thick in the middle and thin at the edges.

Concave lens: A lens that is thin in the middle and thick at the edges.

2. Explore: The effect of lenses on light

1. Convex lens: Convex lens converges light, so convex lens is also called converging lens.

2. Concave lens: Concave lens diffuses light, so concave lens is also called divergent lens.

Think about it, can you change the light emitted by a small light bulb into parallel light?

1Light rays parallel to the principal optical axis converge at the focus

2 The light passing through the focus is refracted by the convex lens and becomes parallel to the main optical axis.

3. The direction of light passing through the optical center remains unchanged after being refracted by the convex lens.

Think about it?

(1) What does the light incident through the focus look like after passing through the convex lens?

(2) What happens to the light incident on the virtual focus on the opposite side of the concave lens after passing through the concave lens?

in conclusion:

(1) The light passing through the focus of the convex lens is refracted and emitted parallel to the main optical axis. Therefore, parallel light can be obtained by using a convex lens!

(2) The light incident on the virtual focus on the opposite side of the concave lens is refracted and emitted parallel to the main optical axis!

6. Knowledge extension: the meaning of "convergence" and "divergence" in optics.

The refracted light rays are closer to the main optical axis relative to the red dotted line, which is called "convergence".

The refracted light rays move away from the main optical axis relative to the straight line of the red dotted line, which is called "divergence".

Do you know how to find focus and measure focal length?

Let the convex lens face the sun and place a piece of paper on the other side of it. Change the distance between the lens and the paper until the light spot on the paper becomes the smallest and brightest. This is the focus of the convex lens.

Use a scale to measure the distance from the smallest and brightest spot to the convex lens. This is the distance of the convex lens.

practise

1. Convex lenses have a _________ effect on light. Concave lenses have a _________ effect on light. Reading glasses are _________. Glasses for myopia are _________.

2. In ancient my country, some people ground ice into convex lenses and made fire against the sun. This took advantage of the _________ effect of convex lenses on light.

3. Which of the following statements is correct ( )

A. Convex lenses have a divergent effect on light, so they are also called divergent lenses.

B. Concave lenses have a converging effect on light, so they are also called converging lenses.

C. A convex lens has two real focal points, and a concave lens has two virtual focal points.

D. The distance between two focal points is called focal length.

life physics society

1. The staff exploring in the Arctic have lost fire. Please find a way to obtain fire for the explorers working in the ice and snow, and solve their worries.

2. Do you know who caused the trouble?

One day, after a heavy rain, the puppy Beibei was lying on the hay in his nest. The top of the kennel was built with thin plastic to protect it from the rain. At this time, a layer of water had accumulated on the plastic. The sky was sunny, and the sun shone through the water on the dog, making it very warm and comfortable. , suddenly, Beibei's tail caught fire, making it jump up and down in pain...

3. When going on an outing, why can't you throw the beverage bottles with liquid left in the woods?

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For more information about the PPT courseware "Lens and its Applications Lenses", please click the Lenses and Their Applications ppt lens ppt tag.

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Update Time: 2024-09-10

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

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