"Central Projection" PPT Courseware 2

Description

"Central Projection" PPT Courseware 2

teaching objectives

Through rich examples, you can understand the projection phenomenon in life, understand the concept of central projection, and feel the relationship between the object under the central projection and its projection.

By operating and observing the shadows of thin bamboo sticks and parallelogram pieces of paper under the light, students can abstract the rules of the center projection of points, line segments, and parallelograms to develop students' spatial concepts and reasoning abilities.

Gallery

Shadows can be seen everywhere. Can you give some examples in life where objects form shadows under the illumination of light?

shadow puppet

Shadow puppetry is a performing art that uses light to reflect the shadows on the screen (projection surface).

Research activity one

Independent learning: Use the textbook to understand the definitions of projection, projection line, projection surface, and central projection

projection

Under the illumination of light, the shadow of an object in space falling on a plane can reflect the shape and size of the object. This phenomenon is called projection.

central projection

The projection formed by the light rays emitted from the same point (point light source) is called the central projection. The point light source is called the center of projection.

summary properties

When a plane figure is parallel to the projection surface, its projection on the projection surface is a plane figure similar to it. The similarity ratio is equal to the ratio of the distance from the projection center to the plane figure to the distance from the projection center to the projection surface. At this time, the projection The area is greater than the area of ​​the plane figure;

When a plane figure is tilted to the projection surface, the shape and size of the projection will change. It may be a plane figure that is not similar to it. Its area may be greater than the area of ​​the plane figure, or it may be equal to or smaller than the area of ​​the plane figure.

When a plane figure is perpendicular to the projection surface, its projection is a line segment.

Interactive exploration

Is the center projection of the intersecting line still the intersecting line? Is the center projection of a parallel line still a parallel line? Are the center projections of equal line segments still equal? for example

Practice in class

1. As shown in the picture, Xiao Liang is walking under the lamp at night. When Xiao Liang walks from A to B, his shadow on the ground ( )

A. Gradually become shorter

B. Gradually lengthen

C. First become shorter and then become longer

D. First become longer and then become shorter

2. The shadows of two objects under the same light can be ( )

A. Same direction B. Different directions

C. Opposite direction D. All of the above are possible

Reflection and improvement

Projection Projection Line Projection Surface

Central projection: The light emitted by light bulbs and candles can be seen as emitting from a point. The projection formed by such light is called central projection. Light bulbs and candles are called point sources of light.

Properties of central projection

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For more information about the "Central Projection" PPT courseware, please click the Center Projection PPT tab.

"Parallel Projection and Central Projection" Projection and View PPT:

"Parallel Projection and Central Projection" Projection and View PPT Part 1 content: Learning objectives can use specific examples to explain the concepts of what is projection, what are projection lines and projection planes; understand the concepts of parallel projection and central projection; explain through examples illustrate..

"Central Projection" PPT courseware:

"Central Projection" PPT courseware Learning objectives: 1. Experience the process of practice and exploration, understand the meaning of central projection, and master the nature of central projection. 2. Through observation and imagination, you can abstract the rules (key points) of the center projection of points, line segments, and plane graphics. 3...

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Update Time: 2024-09-07

This template belongs to Mathematics courseware Qingdao Edition Ninth Grade Mathematics Volume 2 industry PPT template

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