"End of Chapter Summary and Improvement" Light Phenomenon PPT

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"End of Chapter Summary and Improvement" Light Phenomenon PPT

Part One: Key Breakthroughs

Types Reflection and refraction of light

1. Which of the following analysis of light phenomena is reasonable (D)

A. The reflection of the Science City buildings in Xinglong Lake is a phenomenon of light refraction.

B. The giant panda on the outer wall of a tall building can be seen by the eyes because the light emitted by the eyes reaches the object.

C. We can see tall buildings at night from different directions because of the refraction of light.

D. Rainbows appear in the sky after rain because water droplets refract light of different colors to different degrees.

2. There are two electric lamps in a dark room. Only one lamp is lit, but people can see the unlit bulb. For the following light path diagram drawn by "seeing an unlit light bulb", the correct one is (C)

3. (Hubei High School Entrance Examination) Which of the following statements about the reflection and refraction of light is correct (A)

A. Mirage is formed due to the refraction of light

B. Light slants from the air to the calm water surface. The reflection angle is equal to the incident angle, but the refraction angle is greater than the incident angle.

C. The reflectors set up at the corners where the field of vision is not wide are concave mirrors.

D. Whether it is reflection or refraction, the optical path is irreversible.

End-of-Chapter Summary and Improvement PPT, Part 2: Experimental Activities

Experiment 1: Explore the law of light reflection

1. Experimental equipment: cardboard, protractor, plane mirror, laser pointer, etc.

2. Experimental device: as shown in the figure.

3.Experimental conclusion

In the reflection phenomenon, the reflected ray, the incident ray and the normal line are in the same plane; the reflected ray and the incident ray are located on both sides of the normal line respectively; the reflection angle is equal to the incident angle.

[For training]

1. Shown in the picture is the experimental device used by Xiao Bin to “explore the law of light reflection”. Place a plane mirror on a horizontal table, and then stand a piece of cardboard ENF vertically on the plane mirror. The straight line ON on the cardboard is perpendicular to the mirror surface.

(1) If the cardboard is not placed perpendicular to the plane mirror, when the light is incident against the cardboard E, the reflected light cannot be seen on the cardboard F (optional "can" or "cannot");

(2) Xiao Bin wants to explore whether the reflected light and the incident light are in the same plane. The next operation is to slowly rotate the cardboard F backward with the normal ON as the axis;

(3) Change the direction of the incident light, and then observe several sets of incident angles and reflection angles. The purpose of this is to find general rules;

(4) For each determined incident ray, the reflected ray is unique.

Experiment 2: Explore the characteristics of plane mirror imaging

1. Experimental equipment: two identical candles, thin glass plates, scales, white paper, pens, light screens, etc.

2. Experimental device: as shown in the figure.

3. Experimental steps

(1) Spread white paper on a horizontal table and place flat glass vertically on the white paper.

(2) Take two identical candles and place them on the front and rear of the glass plate.

(3) Light candle A in front of the glass plate, observe through the glass plate, and move candle B behind the glass plate until it completely coincides with the image of candle A in front of the glass plate.

(4) Use a pen to mark the positions of the front and rear candles, and draw the position of the glass plate.

(5) Remove candle B, place a light screen at this position, and observe whether the image of candle A can appear on the light screen.

(6) Use the scale to measure the distances between candle A and candle B and the glass plate.

(7) Remove the candle and the glass plate, use a pen to connect the positions of candles A and B, and observe the positional relationship between the line connecting candles A and B and the glass plate.

(8) Move candle A and repeat the above experiment.

(9) Organize and place equipment neatly.

4.Experimental conclusion

(1) The size of the image formed by the plane mirror is equal to the size of the object.

(2) The distance from the image to the plane mirror is equal to the distance from the object to the plane mirror.

(3) The line connecting the object and the image is perpendicular to the plane mirror.

[For training]

2. In the experiment of "Exploring the Characteristics of Plane Mirror Imaging", the experimental device is as shown in the figure. A and B are two identical candles, and C is a 3 mm thick glass plate.

(1) In the experiment, it was found that candle A formed two images, and the distance between the two images was greater than (optional "greater than", "equal to" or "less than") 3 mm;

(2) In the experiment, if candle B is also lit and placed in the position of the image of candle A, the image of candle A seen in front of the glass will not be clear. The reason is that after candle B is lit, the back of the glass plate is too bright;

(3) In order to let Xiao Liang, who is sitting on the right side, also see the image of candle A, Xiao Ming moves the glass plate a certain distance to the right along a straight line. During this process, the image of candle A will not appear (optional "will"). or "won't") pan right.

End-of-Chapter Summary and Improvement PPT, Part Three: Connection between Junior High School and High School

Total reflection: Also known as total internal reflection, it refers to the phenomenon that when light is emitted from an optically dense medium to the interface of an optically sparse medium, all light is reflected back into the original medium.

When light enters an optically sparse medium from an optically dense medium, it is refracted away from the normal line, as shown in the figure. When the incident angle increases to a certain situation, the refraction line proceeds along the surface, that is, the refraction angle is 90°. This incident angle is called the critical angle. If the incident angle is greater than the critical angle, there will be no refraction and all light will be reflected back to the optically dense medium. This phenomenon is called total reflection. When light passes from an optically sparse medium to an optically dense medium, total reflection does not occur because the light is refracted close to the normal.

[For training] When light enters from a medium with high density into a medium with low density, the refraction angle is greater than the incident angle. Then when the incident angle gradually increases, we find that the refraction angle also becomes larger and larger. If the incident angle increases to At a certain angle, the refraction angle reaches 90°. When it increases further, the refracted light will disappear. This phenomenon is called total reflection, and this angle is called the critical angle. Triangular prism ABC made of glass with a critical angle of 42°, ∠B=20°, ∠C=90°, a beam of light is incident perpendicularly to the AC surface, as shown in the figure, the number of total reflections it undergoes in the prism is (A)

A. 2 times B. 3 times

C. 4 times D. 5 times

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Update Time: 2024-10-20

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