"Reflection of Light" Light Phenomenon PPT

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"Reflection of Light" Light Phenomenon PPT

Part One: Preview Perception

1. The law of reflection of light

1. Reflection conditions.

Light is reflected when it encounters desktops, water, and many other surfaces.

2. Nouns related to reflection (as shown in the picture).

(1) Normal: a straight line perpendicular to ______________.

(2) Incident angle: the angle between ______________ and ___________.

(3) Reflection angle: the angle between ______________ and ___________.

3. Content.

(1) Same plane: In the phenomenon of reflection, _______________ rays, _______________ rays and _______________ lines are in the same plane.

(2) Two sides: the reflected light and the incident light are located on both sides of ______________.

(3) Angles are equal: angle ______________ is equal to angle ______________.

(4) The path is reversible: In the reflection phenomenon, the light path is __________.

2. Specular reflection and diffuse reflection

1. Figure a shows the ______________ reflection, and Figure b shows the ______________ reflection.

2. Comparison of two reflections:

common ground

When each light ray is reflected, it obeys the law of __________; the light path is __________

difference

The reflective surface is a smooth plane, and the parallel beam is still

The reflective surface is rough and uneven, and the parallel beam is reflected and directed towards

Reflection of light PPT, part 2: interactive classroom understanding

law of light reflection

1. One reflected ray corresponds to one incident ray.

2. Note: "The reflection angle is equal to the incident angle" cannot be said to be "the incident angle is equal to the reflection angle", because there is incidence first and then reflection, and the reflected light changes with the change of the incident light.

3. The changes in the relationship between the two angles are corresponding. When the incident angle increases (decreases), the reflection angle also increases (decreases); when the incident angle is 0, the reflection angle is also 0, that is, the reflected light, incident light The three lines of light and normal coincide.

4. The normal is the angle bisector of the angle between the reflected ray and the incident ray.

[Example] Xiao Ming’s mother’s mobile phone fell under the sofa. There was no flashlight. Xiao Ming used a plane mirror to reflect the light and found the mobile phone. The reflected ray and incident ray have been marked in the picture on the right. Please draw the position of the plane mirror in the picture and keep the traces of the drawing.

Tip: Draw according to the law of light reflection, the idea is as follows:

Analysis: According to the law of light reflection, the incident ray, reflected ray and normal line are in the same plane, and the reflection angle is equal to the incident angle. The angle bisector of the angle between the incident light and the reflected light is the normal line. The normal line is drawn through the reflection point, and the perpendicular line drawn from the normal line is the mirror surface.

Answer: As shown in the picture

Reflection of light PPT, Part 3: Try the application

1. The law of reflection of light

1. Regarding the reflection of light, which of the following statements is wrong ()

A. The reflected ray is in the plane determined by the incident ray and the normal

B. Reflected light and incident light are separated on both sides of the normal line

C. The angle of incidence is greater than the angle of reflection

D. The angle between the incident light and the mirror increases and the reflection angle decreases

2. Draw the reflected ray of incident light AO in the figure, and mark the reflection angle (indicated by the letter β).

This question tests students' ability to complete a light path diagram. The incident ray is given in the diagram and allows us to make a reflected ray. When drawing the diagram, we must first find the incident point, draw a dotted line perpendicular to the plane mirror along the incident point as the normal, and then according to the reflection angle Make a reflected ray equal to the incident angle, and mark the reflection angle β as required.

2. Specular reflection and diffuse reflection

3. Regarding specular reflection and diffuse reflection, which of the following statements is incorrect ()

A. Whether it is specular reflection or diffuse reflection, there is only one reflected light corresponding to one incident light.

B. Every ray of light reflected by the mirror follows the law of light reflection.

C. The light reflected by the mirror must be parallel

D. When the incident light rays are parallel to each other, the reflected light rays after diffuse reflection are not parallel to each other.

4. (2018·Yunnan Yuxi Simulation) Some blackboards will produce a "reflective" phenomenon and the characters cannot be seen clearly. This is because the light emitted from the blackboard is __________ than the light emitted from the chalk characters __________ (optional) "strong" or "weak").

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Update Time: 2024-07-25

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

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