"Refraction of Light" Light Phenomenon PPT Download

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"Refraction of Light" Light Phenomenon PPT Download

The first part: sorting out new knowledge

1. Refraction of light

Refraction of light: When light is incident obliquely from one medium into another medium, ________ is deflected. This phenomenon is called refraction of light.

[Explanation]When light hits the interface of two transparent substances, reflection and refraction often occur at the same time, as shown in the figure.

[Note]Whether it is the incident angle, reflection angle or refraction angle, it refers to the angle between the corresponding light ray and the normal.

[Expansion]"Reflection and Refraction"

① Light is reflected and refracted at the interface of the two media at the same time, so the brightness of the reflected light and refracted light is darker than the incident light.

② When reflection occurs, the propagation speed of light remains unchanged; when refraction occurs, the propagation speed of light changes because light propagates in different media at this time.

2. Laws of refraction of light

1. The law of refraction of light

When light is incident obliquely from the air into water or other media, the refracted ray is deflected in the normal direction, and the refraction angle is smaller than the incident angle; when the incident angle increases, the refraction angle also increases (when the incident angle decreases, the refraction angle also increases decrease). When light is incident vertically from air into water or other media, the direction of propagation does not change.

2. As shown in Figure 4-4-2, the refraction phenomenon of light also follows the principle of light path ______.

3. The relationship between the refraction angle and the incident angle in the refraction of light

(1) The refraction angle increases (or decreases) as the incident angle increases (or decreases). (As shown in Figure 4-4-3)

(2) When light is incident obliquely from a medium with a high propagation speed into a medium with a low propagation speed, the refraction angle ______ the incident angle.

(3) When light is incident obliquely from a medium with a small propagation speed into a medium with a high propagation speed, the refraction angle ______ the incident angle.

3. When light propagates in the same non-uniform material, the direction of propagation continuously changes, which is also a refraction phenomenon. Mirages, "blinks" of stars, etc. are all formed by the refraction of light, which bends the propagation path of light.

Refraction of light PPT, part 2: application examples

Type 1: Exploring the laws of refraction of light

Example 1: A student is doing an experiment on "exploring the refraction characteristics of light". Figure 4-4-6 shows the optical path of light from air to water. In the experiment, it was found that the incident ray, the refracted ray and the normal line are in the same plane, and the refracted ray and the incident ray are located on both sides of the normal line respectively. The following data were also obtained through the experiment:

(1) Analyzing the data in the table, we can draw the following conclusions:

①When light slants from the air to the water surface, _____ and ______ phenomena will occur at the same time.

② When light slants from the air to the water surface, the relationship between the refraction angle and the incident angle is: _______________________________________________, and the refraction angle _______ (optional "greater than", "less than" or "equal to") the incident angle; when the light is vertically incident from the air When reaching the water surface, the refraction angle is equal to zero. The student summarized the refraction characteristics of light based on the findings and conclusions in the above experiment ②.

(2) Please comment on the process by which this student obtained the refraction characteristics of light through the above-mentioned research experiment. Are there any shortcomings? Answer: ______ (please fill in “yes” or “no”); please briefly explain the reason: _______________________________.

[ Analysis According to the data in the table, it can be seen that when the incident angle increases, the refraction angle also increases. When light is vertically incident from the air to the water surface, the incident angle is zero, and the refraction angle is also equal to zero. According to the experimental process, we should also conduct refraction experiments between various other transparent media, and then summarize and draw conclusions. Therefore, the experimental exploration process is incomplete and has shortcomings.

[ Summary of the rules ③Light can also be refracted in the same medium. At this time, the medium should be a non-uniform transparent medium.

Type 2 Application of the law of refraction of light

Example 2 As shown in Figure 4-4-6, Xiao Ming accompanied his grandfather to the lake to spear fish. Xiao Ming threw the steel fork in the direction of the fish he saw, but he always failed to reach the fish. Among the four light path diagrams shown in Figure 4-4-7, the one that can correctly explain the reason why the fish cannot be caught is ()

[ Analysis , what you see is a virtual image of the fish becoming shallower. Experienced fishermen always aim their harpoon just below the fish they see.

[Summary of rules]The position of the fish in the water seen from the shore is above the actual position of the fish, and the position of the treetops on the shore seen from the water is above the actual position of the treetops. Therefore, we can summarize it in one sentence: Whether looking at objects in the water from the shore or looking at objects on the shore from the water, the virtual image seen is above the actual position of the object.

Example 3 As shown in Figure 4-4-9, light is reflected and refracted at the same time at the interface CD between glass and air. The following statement is correct ()

A． The angle of incidence is 40°, and air is on the left

B. The angle of incidence is 50°, and air is on the right

C. The refraction angle is 20°, and the right side is glass

D. The refraction angle is 70°, the left side is glass

[Method Guidance]Discrimination of Comprehensive Optical Path of Light Reflection and Refraction

① First, determine the reflected ray and incident ray according to the reflected ray and incident ray being located on both sides of the normal and in the same medium; then determine the incident angle and reflection angle according to the direction of the arrow.

②According to the fact that the refracted ray and the incident ray are also located on both sides of the normal line, but in two different media, determine the refracted ray and thereby determine the refraction angle.

③According to the relationship between the incident angle and the refraction angle and "when light is incident obliquely from air into other transparent media, the refraction angle is smaller than the incident angle", it can be determined which side of the interface is air and which side is other transparent media.

Type 3: Light refraction mapping

Example 4 2018·Xinjiang Based on the incident light ray and normal line in Figure 4-4-9, draw the general direction of the corresponding refracted light ray.

[ Analysis Refract light.

[Method guidance]Light refraction drawing techniques

When the incident light is known to be used as a refracted ray, follow the following steps to draw the diagram: ① Find the incident point and draw a normal line through the incident point; ② Draw the refracted ray according to the relationship between the refraction angle and the incident angle.

Refraction of light PPT, Part 3: Class feedback

1. Life is all about physics. Look at the beautiful scenery around us. The following description of the scene belongs to the refraction of light: ()

A． Reflections of sculptures in the square in the pool

B. Shadows of people running on the sports field

C. The sunlight shines through the leaves and falls on the ground

D. We saw the fish swimming happily in the lake

2. A beam of light is shot obliquely from water to air, and reflection and refraction occur at the same time. The correct one in the following light path diagram is ()

3． As shown in Figure 16-2, in the experiment of "exploring the law of refraction of light", Xiaomi folded the movable cardboard showing the refracted light backwards and found that no refracted light could be seen on the cardboard. This phenomenon can be explained ( )

A． When the cardboard is folded back, the refracted rays disappear

B. The refracted ray and the incident ray are separated on both sides of the normal

C. When light is refracted, the light path is reversible

D. The refracted ray, incident ray and normal are in the same plane

4. Figure 16-3 shows the optical path of light slanting from air into water. The refracted light is ______, the incident angle is ______, the reflection angle is _____, and the refraction angle is ______.

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Update Time: 2024-07-30

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

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