"Reflection of Light" Light Phenomenon PPT Courseware 8

Description

"Reflection of Light" Light Phenomenon PPT Courseware 8

1. Why can we see objects such as the sun and electric lights?

The light from the sun and electric lamps directly enters the human eyes and causes vision.

2. Why can we still see classrooms, people, books and other objects that do not emit light themselves?

We can see non-luminous objects because the light reflected by the objects enters our eyes.

1. Reflection of light

When light is emitted from one medium to the surface of another medium, the propagation phenomenon of part of the light returning to the original medium is called reflection of light.

2. The law of reflection of light

Ask the question: What rules does light follow when it is reflected?

Designing and conducting experiments:

1. Concept:

Incident point: The intersection point of the incident ray and the reflecting surface. (0)

Incident ray: ray of light hitting a reflective surface. (A0)

Reflected light: light reflected from a reflective surface. (0B)

④Normal: the perpendicular to the reflecting surface passing through the incident point 0. ON

⑤Incidence angle: The angle between the incident light and the normal. (i)

⑥Reflection angle: The angle between the reflected light and the normal line. (r)

Emphasis: Incident light and reflected light have directions. When expressed by letters, the letters should be stated along the propagation direction of the light. For example, the incident light is AO and the reflected light is 0B; the normal line is to scientifically and accurately describe the reflected light and incident light. An "auxiliary line" introduced due to the positional relationship of light, usually represented by a dotted line,

It has no specific physical meaning; the reflection angle and the incident angle are both the angle between the light and the normal, not the angle with the reflective surface.

2. Law of reflection of light:

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

Clever trick: three lines are coplanar, the normal line is in the middle, and the two angles are equal.

Understanding: The description of the law of reflection of light is strictly logical. The reflected light is formed by the incident light being reflected by the reflective surface, that is, the incident light determines the reflected light. There is a causal relationship between the two. When describing the content of the law, it cannot be said as "incident angle" "Equal to the angle of reflection", there is the angle of incidence first and then the angle of reflection. The angle of reflection exists due to the existence of the angle of incidence, so it should be said that "the angle of reflection is equal to the angle of incidence".

Conditions for reflection to occur: at the interface of two media

Place of occurrence: point of incidence;

Result: Return to the original medium;

Rule: The reflection angle increases with the incident angle and decreases with the incident angle.

3. Reversibility of optical path

What would we see if we let reflected light hit a plane mirror in the opposite direction of the incident light?

In the phenomenon of reflection, the light path is reversible.

Student A can see the eyes of classmate B through the plane mirror, then classmate B can see the eyes of classmate A. (fill in "can" or "cannot")

4. Specular reflection and diffuse reflection-----both follow the law of reflection of light

1. After parallel incident light rays hit a smooth mirror surface, the reflected light rays are still parallel. This reflection is called specular reflection.

2. After parallel incident light rays hit the uneven surface, the reflected light rays are emitted in all directions. This reflection is called diffuse reflection.

We can see non-luminous objects from all directions because light is diffusely reflected on the object.

Class summary

1. Reflection of light: When light is emitted from one medium to another medium, part of the light returns to the original medium.

2. The law of reflection of light

3. Reversibility of light path: In the phenomenon of reflection, the light path is reversible.

4. Specular reflection and diffuse reflection: both obey the law of light reflection.

5. Application of light reflection: periscope

Classwork:

1. When you sit in the classroom, you can see the words on the blackboard from all directions because the light is ____ reflected on the blackboard. At this time, every light ray obeys the ____ law.

2. The screen showing the movie should be: ( )

A. Convergence of light B. Divergence of light

C. Diffuse reflection of light D. Specular reflection of light

3. When the reflected light makes an angle of 400 with the plane mirror, the incident angle of the incident light is ( )

A. 900 B. 400

C、500 D、800

4. Draw the reflected rays or incident rays in each of the following figures

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For more information about the "Reflection of Light PPT" PPT courseware, please click on the "Reflection of Light PPT Light Phenomenon ppt" tab.

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Update Time: 2024-09-08

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

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