"Dispersion of Light" Light Phenomenon PPT Courseware 9

"Dispersion of Light" Light Phenomenon PPT Courseware 9

Review the past and learn the new

1. When light enters glass obliquely from the air, the refracted light is deflected in the direction of the ______ normal. (Fill in “closer” or “away”)

2. A beam of light strikes a glass prism obliquely (as shown below), and draw the refraction of the light.

teaching objectives

1. Know the dispersion phenomenon of light and the composition of white light.

2. Know the different phenomena of color and light mixing;

Know what factors determine the color of an object.

Let a beam of sunlight shine on a prism. What happens to the light emerging from the prism?

1. Sunlight is decomposed into seven colors of red, orange, yellow, green, blue, indigo and violet.

2. Sunlight is not monochromatic light, but a mixture of various colored lights - complex colored light.

3. All colors of light are refracted toward the bottom edge, with red light having the smallest deflection and violet light having the largest deflection.

Question: How is a rainbow formed?

Answer: There are a large number of tiny water droplets suspended in the sky after a rain. When sunlight hits these small water droplets, dispersion occurs and is broken down into brilliant seven-color light. Therefore, sometimes we can see the rainbow created by sunlight and small water droplets.

Tracking exercises

1. After passing through a prism, sunlight is decomposed into seven color bands of _____, _____, _____, _____, _____, _____, _____. This is the phenomenon of _____.

2. The dispersion phenomenon of light shows that white light is composed of __________.

3. A rainbow is caused by sunlight being _____ by water droplets in the air during its propagation.

4. Mao Zedong’s poem “Red, orange, yellow, green, indigo, blue, purple, who holds the colors and practices dancing in the air” mainly involves physical knowledge: __________.

5. After the train starts, "white gas" is discharged from the exhaust hole. Passengers sitting on the train can see a rainbow through the "white gas" if they are facing the slanting sunlight. Why is this?

Polychromatic light of sunlight is the refraction that occurs when sunlight hits "white gas". The "white gas" has different deflection abilities for different colors of light, and disperses the white light emitted by the sun into colored light, so you will see a "rainbow" .

1. Color of transparent objects

A transparent object transmits only light of the same color as it

The color of a transparent object is the same as the color of the transmitted light.

2. Color of opaque objects

An opaque object reflects only light of its own color.

The color of an opaque object reflects the light it reflects.

Note: White objects reflect various colors of light. Black objects absorb various colors of light and do not reflect light at all.

Tracking exercises

1. The color of an opaque body is determined by its _______. When sunlight shines on a black screen, the screen appears __ color.

2. The screen used to play movies is usually made of rough white cloth. This is because ( )

A. It can absorb various colors of light

B. It can refract light

C. It can reflect various colors of light and diffuse reflection occurs.

D. None of the above statements are correct

3. Write blue words on white paper and see them under blue light ( )

(A) The paper is white and the words cannot be seen clearly;

(B) The paper is white and the words can be read clearly;

(C) The paper is blue and the words are black, so you can see them clearly

(D) The paper is blue and the words are also blue and cannot be seen clearly.

4. A piece of paper looks red under a certain light, then ( )

(A) The paper must be red; (B) The paper must be white;

(C) The light bulb must be red; (D) It is impossible to determine.

Compliance testing

1. Which of the following phenomena belongs to the dispersion phenomenon of light ( )

A. The rainbow in the sky after the rain B. The moon in the water

C. Blackboard "reflection" D. Small hole imaging

2. Among various colors of light, what are called the three primary colors of light are ( )

A. Red, green, blue B. Red, yellow, blue

C. red, yellow, green D. yellow, green, blue

3. From April 2nd to 5th, our city, as a high-yielding rapeseed area in the country, held the "China Jingmen First Rapeseed Flower Tourism Festival". At that time, yellow rapeseed flowers can be seen everywhere in the countryside, and the strong fragrance of rapeseed flowers can always be smelled. We can see the bright yellow rapeseed flowers because the rapeseed flowers can ________ yellow light.

4. On Mount Tai, one of the "Five Mountains", the "Buddha's Light" spectacle has appeared many times in history. According to eyewitnesses: "Buddha's Light" is a huge colorful halo, exactly the same as the common rainbow colors. The main reason for the formation of "Buddha's Light" is ( )

A. straight line propagation

B． pinhole imaging

C. reflection of light

D． dispersion of light

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