"Color of Objects" Light Phenomenon PPT Courseware

"Color of Objects" Light Phenomenon PPT Courseware

【Experience】Dispersion of light

Activity 1: Prepare water, container, plane mirror, and paper screen. Place the device as shown in the figure. Adjust the angle of the mirror so that the sun's rays are refracted onto the white paper screen. Observe the color of the light on the paper screen.

Activity 2: Put the CD in the sun and observe the colors you see.

(1) In Activity 1, after white light is reflected by a plane mirror in the water and refracted by the water, it will form a ________ (optional "white" or "color") light band.

(2) In Activity 2, the CD appears in color _______ (optional "yes" or "no") placed under sunlight.

Tips: (1) Color (2) Skilled

pre-study questions

1. What is the dispersion of light? What does the dispersion of light mean?

2.What is the principle of three primary colors?

3. What determines the color of an object?

Explore 1 Dispersion of light

Combine the activities in "Experience" and the experiment to study the decomposition of white light, and think about the following questions.

1. After white sunlight passes through a prism, it will be decomposed into seven colors of light. This shows what?

Tip: White light is decomposed into seven colors of red, orange, yellow, green, blue, indigo and violet after being refracted by a prism. Explain that white light can be decomposed and is made up of a mixture of various colored lights.

Reference answer: red, orange, yellow, green, blue, indigo, violet This shows that white light is a mixture of various colors of light.

2. How is the rainbow formed after the rain?

Tip: A rainbow is a band of light composed of red, orange, yellow, green, blue, indigo and violet light. It is formed after sunlight is refracted by small water droplets suspended in the air.

Reference answer: A rainbow is formed after sunlight is refracted by small water droplets.

Explore 2 The three primary colors of light and the color of objects

Based on your own life experience, think about the following questions:

1. The seven-color light decomposed by the inverted prism combines into _______ after passing through another upright prism.

Reference answer: white light

2. As shown in the figure, the three colors of red, green and blue light can be mixed into ______ light. Therefore, it can be seen that the "three primary colors" of light are _________, and the reason why they are called three primary colors is because_______________________________.

Reference answer: white red, green, blue

The three colors of light, red, green and blue, cannot be mixed with other colors of light, while other colors of light can be made by properly mixing the three colors of red, green and blue.

3. If you let the white sunlight pass through the red glass, what you will see is ________ color. What does this mean?

Tip: The color of a transparent object is determined by the transmitted colored light. Glass is red because it only transmits red light and absorbs light of other colors. So the glass you see is red.

Reference answer: red This means that transparent objects only transmit light of the same color as themselves.

Knowledge summary

1. Dispersion of light

1. Prism: The glass triangular prism with ________ in the middle.

2. Definition: The phenomenon that sunlight is refracted by a prism to form a light band composed of _______________ equal-colored light.

3. Explanation: White light is not _________, but is composed of _________ light.

2. The principle of three primary colors of light

1. Concept: Most of the colored lights in nature can be made by mixing three kinds of colored lights in different proportions.

2. Example: The colorful pictures on the color TV screen are formed by the superposition of ________ colored light.

3. Color of objects

1. The color of a transparent object: determined by the color light it can _____. Colorless transparent objects allow _______ light to pass through.

2. The color of an opaque object is determined by its _____ color light.

Test point 1 Dispersion of light

[Typical example 1] Let a beam of sunlight shine on a white screen through a prism, and a colored light strip will be formed on the white screen. The colors of the light from top to bottom are _____ seven different colors. This phenomenon is called The ________ of light is caused by the different degrees of deflection of light of different colors contained in white light when they pass through a prism (optional "reflection" or "refraction").

[Idea Guide] The key points to answer this question: (1) Know the seven colors of light after dispersion of sunlight; (2) Refraction occurs when sunlight enters another medium from one medium.

[Exquisite analysis] Sunlight is white light. It is decomposed into seven colors of light after passing through a prism. This phenomenon is called dispersion of light. Sunlight is refracted when it enters the prism from the air, and finally the light is ejected from the prism into the air. Refraction occurs. Since light of different colors has different degrees of deflection when passing through a prism, red light has the smallest degree of deflection and violet light has the largest degree of deflection. Therefore, the colors on the light screen from top to bottom are red, orange, yellow, green, blue, Indigo, purple.

Answer: red, orange, yellow, green, blue, indigo, violet dispersion refraction

Test point 2 Color of objects

[Typical Example 2] (2012·Guangdong High School Entrance Examination) When an advertising company was shooting a fruit advertisement, in order to pursue a certain artistic effect, it used red light to illuminate red apples and yellow bananas in white porcelain plates in the darkroom. A photographer standing nearby will see ()

A. The apple is black, the porcelain plate is white, and the banana is black

B. The apple is red, the porcelain plate is black, and the banana is black

C. The apple is black, the porcelain plate is red, and the banana is red

D. The apple is red, the porcelain plate is red, and the banana is black

[Idea Guide] Grasp white and red objects to reflect red light, and objects of other colors can absorb red light to solve the problem.

【Exquisite analysis】Choose D. This question tests the knowledge about color and light. The color of an opaque object is determined by the color of light it reflects. A certain color only reflects a certain color of light, a white object can reflect all colors of light, and a black object does not reflect at all. When red light shines on a white porcelain plate, it reflects red light and appears red; when it shines on a red apple, it also reflects red light and appears red; when it shines on a yellow banana, it does not reflect red light and appears black.

1. In the sky after rain, a beautiful rainbow sometimes appears. Which of the following statements about "rainbow" is incorrect ()

A. It is the refraction phenomenon of light

B. It is the dispersion phenomenon of light

C. It is the reflection phenomenon of light

D. It is formed due to a large number of small water droplets suspended in the air.

[Analysis] Choose C. This question examines the phenomenon of dispersion in nature. A rainbow after a rain is caused by the dispersion of light caused by the refraction of sunlight after passing through a large number of small water droplets suspended in the air.

2. (2012·Shanghai High School Entrance Examination) Among the following types of monochromatic light, one of the three primary colors is ()

A.Red light B.Orange light C.Yellow light D.Purple light

[Analysis] Choose A. This question examines the composition of the three primary colors of color and light. After mixing the three colors of red, green and blue in different proportions, light of various colors can be produced, so red, green and blue are called the three primary colors of light. Therefore choose A.

3. An actor is performing on the stage. When the red follow-up light above the stage shines on her, the audience sees her in a gorgeous red costume; when the lighting operator switches to a green follow-up light on her, the audience sees her. The top is green and the skirt is black. So, the actual color of the actor’s costume is ()

A.The top and skirt are both red

B. The top and skirt are both green

C. The top is green and the skirt is black

D. The top is white and the skirt is red

[Analysis] Choose D. This question tests the judgment of the color of objects. An actor is performing on the stage. When the red follow-up light above the stage shines on her, the audience sees her wearing a gorgeous red costume; when the lighting operator switches to a green follow-up light on her, the audience sees her top If the color is green and the skirt is black, it means that her top can reflect both red light and green light, so her top is white; her skirt can reflect red light but not green light, so her skirt is red. . So choose D.

Project the three primary colors of light onto a white screen in a dark room. The projection situation is as shown in the figure. Area A is ______ color, and the light that occurs on the white screen is ______ (optional "specular" or "diffuse") reflection. .

[Students’ own answers]

①Black ②Mirror surface

[Teacher Comments]

① I didn’t remember clearly that the three primary colors become white light after mixing.

② Misunderstood that the white screen can reflect all colors of light as specular reflection.

【correct answer】

Bai Man

Keywords: light phenomenon teaching courseware, object color teaching courseware, Beijing Normal University version eighth grade physics PPT courseware download, eighth grade physics slide courseware download, light phenomenon PPT courseware download, color of object PPT courseware download, .PPT format ;

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