"Refraction of Light" Light Phenomenon PPT Courseware 7

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"Refraction of Light" Light Phenomenon PPT Courseware 7

【Experience】Understand the refraction of light

Activity 1: Pour water into an empty cup continuously and observe the height of the bottom of the cup.

Activity 2: Insert chopsticks into the water and observe the changes in the chopsticks.

(1) In activity 1, you found that the bottom of the bowl kept changing ______ (choose "shallow" or "deep").

(2) In activity 2, the chopsticks inserted into the water look like ______.

Tips: (1) Shallow (2) Broken (broken)

pre-study questions

1.What is refraction of light?

2. What is the content of the law of refraction of light?

3. What are the common light refraction phenomena in daily life?

Explore 1 the phenomenon of refraction of light

Combined with "experience", think about the following questions

1. According to "experience" and the condition that light propagates in a straight line, when light is emitted from the air into water, the propagation direction of the light will be ______.

Tip: The conditions for light to propagate along a straight line: light propagates along a straight line in the same homogeneous medium; when light is emitted from air into water, the type of medium changes, and the propagation direction of the light will be deflected.

Reference answer: Deflection occurs

2. The picture shows the optical path of light from air to water.

Figure, mark the angle of incidence, refracted ray, and angle of refraction.

①__________ angle

②__________Light

③__________ angle

Tips: ①i is the angle between the incident light and the normal line, which is the incident angle; ② is the light that enters the water from the air and is refracted, which is the refracted ray; ③r is the angle between the refracted light ray and the normal line, which is the refraction angle.

Reference answer: incidence refraction refraction

Exploration 2 Explore the laws of refraction of light

1.Experimental design:

(1) When doing experiments, what methods do you have to show the propagation path of light?

Tip: In order to facilitate the observation of the propagation path of light, there are generally three methods: ① Spray smoke in the air; ② Drop a little milk or blue ink in the water; ③ Place a light screen so that the light is incident close to the light screen.

Reference answers: ① Spray smoke in the air; ② Drop a little milk or blue ink into the water; ③ Place the light screen so that the light is incident close to the light screen.

(2) How to study the positional relationship between refracted rays, incident rays, and normals in experiments?

Tip: Use a light screen to display the light path, observe the positional relationship between the refracted light, the incident light, and the normal line. Turn the light screen at a certain angle and observe whether there is any refracted light on the light screen. If not, it means that the three are in the same plane.

Reference answer: Turn the light screen at a certain angle and observe whether there is any refracted light on the light screen.

(3) In the experiment, how to explore the relationship between the refraction angle and the incident angle?

Tip: Keep changing the direction of the incident light and observe the changes in the position of the refracted light on the light screen. Measure the angle of incidence and angle of refraction and compare.

Reference answer: Measure multiple sets of incident angles and refraction angles, and compare their sizes.

Knowledge summary

1. The law of refraction of light

1. Refraction phenomenon: the phenomenon in which the direction of propagation of light changes from _______________.

2.Refraction angle: The angle between ________.

3.Refraction rules:

(1) Three lines are coplanar: When light is refracted, _________, _________ and _____

in the same plane.

(2) The two lines are on opposite sides: the refracted ray and the incident ray are located on both sides of _____.

(3) Two-corner relationship

① When light passes from air to water or glass, the refraction angle _____ incident angle

② When light passes from water or glass to air, the refraction angle _____ incident angle

③When the incident angle increases (or decreases), the refraction angle _____ (or _____).

(4) When light hits the interface of two media vertically, the propagation direction is _____, the refraction angle is ____, and the incident angle is equal to ____.

2. Application of the law of refraction of light

1. When looking at an object in a transparent medium such as water or glass from the air, you will feel that the position of the object is ___ (optional "higher" or "lower") than its actual position.

2. Mirage

Test Points Applying the Laws of Refraction of Light to Draw Drawings

[Typical example] (2012 Shiyan High School Entrance Examination) As shown in the figure, a student observes at point A that the image formed by point light source S in the water is at point B. Please draw the optical path of the light emitted from point S through point A. picture.

[Concise Lecture and Analysis] This question examines the drawing of the refraction laws of light. We can see objects because light enters our eyes. Therefore, the image points B and A we see are on a straight line, connecting AB and the water surface at point O. Then this point is the direction of the light emitted by the point light source S. At the incident point of the water surface, SO is the incident ray and OA is the refracted ray.

Answer: As shown in the picture

[Method Summary] Method of drawing using the refraction laws of light

(1) If the incident (refracted) ray is known, make the refracted (incident) ray.

(2) Given the object and image, make a light path diagram

1. (2012·Suzhou High School Entrance Examination) Among the following light phenomena, what is formed due to the refraction of light is ()

[Analysis] Choose C. This question examines the phenomenon of refraction of light. Both immediate effects and total solar eclipses are caused by light propagating in a straight line, reflections are caused by the reflection of light, and the "breaking" of branches extending into the water is a phenomenon of light refraction.

2. When a beam of light slants from the air into the water, if the incident angle gradually increases, the refraction angle　()

A. Gradually decreases and is always greater than the incident angle

B. Gradually increases and is always smaller than the incident angle

C. Gradually decreases and is always smaller than the incident angle

D. Gradually increases and is always greater than the incident angle

[Analysis] Choose B. This question examines the laws of refraction of light. When light enters water obliquely from air, the refracted ray is deflected in the normal direction, that is, the refraction angle is smaller than the incident angle. The refracted light changes with the change of the incident light. When the incident angle gradually increases, the refraction angle also gradually increases.

3. Regarding the refraction of light, which of the following statements is incorrect ()

A. When light enters from one medium to another, the direction of propagation must change.

B. When light is incident obliquely from water into air, the refraction angle is greater than the incident angle.

C. Light is incident from the air into water obliquely. When the incident angle increases, the refraction angle also increases, but it is always smaller than the incident angle.

D. Like the reflection phenomenon of light, the refraction light path is also reversible.

As shown in the figure, point A on the bottom of the lake emits a beam of light diagonally towards the water surface. Please draw the approximate optical path diagram of this beam of light after it enters the air, and mark the refraction angle r.

[Teacher Comments]

①The normal is correct

②The refracted light is wrong and should be kept away from the normal line

③The refraction angle is wrongly marked, it should be the angle between the refracted ray and the normal line

【Correct drawing】

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Update Time: 2024-10-19

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