"Lens" Lens and its applications PPT courseware 4

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"Lens" Lens and its applications PPT courseware 4

Students, what mirrors have you used or seen in your life?

Can cause light to reflect

Full-length mirrors, plane mirrors, reflectors, prisms, magnifying glass lenses, reading glasses, myopia glasses, telescopes, cameras, slide projectors, movie projectors, microscopes and other instruments.

Observe and communicate

What is the difference between the two lenses on your desk? Please tell how they are different.

Method 1: "Touch"

To avoid lens wear or staining, wrap the lens in soft tissue paper before touching it with your hands.

Method 2: "See"

Observe nearby objects through a lens.

1. Convex lenses and concave lenses

1. Convex lens

Lenses that are thick in the middle and thin on the edges

2. Concave lens

Lenses that are thin in the middle and thick on the edges

2. The main optical axis and optical center of the lens

1. Principal optical axis: a straight line passing through the centers of two spheres.

2. Optical center: The optical center is a special point on the main optical axis through which light rays pass through the lens without changing direction. It can be considered that the optical center of a thin lens is at the center of the lens.

3. Effect of lens on light

1. The effect of convex lens on light

Convex lenses have a converging effect on light

Conclusion: Convex lenses have a divergent effect on light, so convex lenses are also called converging lenses.

2. The effect of concave lens on light

Concave lenses diffuse light

Conclusion: Concave lenses have a divergent effect on light, so concave lenses are also called divergent lenses.

5. Three special rays

1. The propagation direction of light passing through the optical center does not change.

2. The light ray parallel to the main optical axis passes through the focus on the opposite side after being refracted by the convex lens. After being refracted by the concave lens, the reverse extension line of the refracted light passes through the virtual focus.

3. The light that passes through the focus of the convex lens is refracted and emitted parallel to the main optical axis. The light incident on the forward extension line through the virtual focus on the opposite side of the concave lens is refracted and emitted parallel to the main optical axis.

1. Given a lens, what methods can you use to determine whether it is a convex lens or a concave lens?

Method one: "touch". It is distinguished by comparing the thickness of the center and edge of the lens. (Note: To prevent the mirror from being worn or stained, wrap the lens with soft tissue paper before touching it with your hands)

Method 2: "Look". Observe nearby objects through a lens and discern whether they appear enlarged or reduced.

Method three: "Photo". Distinguish whether parallel light rays converge or diverge through a lens.

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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: 2024-07-08

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

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