"Reflection of Light" Light Phenomenon PPT Courseware 6

Description

"Reflection of Light" Light Phenomenon PPT Courseware 6

Knowledge review

What is a light source?

Objects that can emit light on their own are called light sources

how light travels

Light propagates in straight lines in the same homogeneous medium

What is the speed of light

The propagation speed of light in vacuum is 3 × 10 8 m/s

What is one light year?

The distance that light travels in one year is 9.46 × 1015 meters

1. Reflection phenomenon of light

When light hits the surface of an object, it is reflected back by the surface of the object (back to the original propagation medium). This phenomenon is called reflection of light.

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

2. The law of reflection of light

Ask a question: What laws follow when light reflection occurs?

guess:

What does the third line have to do with each other?

What's the relationship between the two corners?

our research

experiment procedure:

Step 1: Adjust the cardboard that receives the reflected light and observe whether the reflected light, incident light and normal are in the same plane.

Step 2: Change the position of the incident light and observe whether the reflected light and incident light are on the same side of the normal or on both sides.

Step 3: Measure the sizes of several sets of reflection angles and incident angles, and compare the relationship between the two angles.

The law of reflection of light:

The reflected ray is on the same plane as the incident ray and normal.

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

The angle of reflection is equal to the angle of incidence

Formula: Three lines are coplanar, two lines are separated, and two angles are equal.

1. Among the following idioms, which one can describe the reflection of light ( )

A. Mirage B. Looking at the sky from a well

C.Flower in the mirror D.Immediate effect

2. Among the following statements, which one violates the law of reflection of light ( )

A. The angle of incidence is 0°, and the angle of reflection is also 0°.

B. The incident angle increases by 10°, and the reflection angle also increases by 10°.

C. The incident light ray is close to the normal line, and the reflected light ray is also close to the normal line.

D. The angle of incidence is equal to the angle of reflection

3. The angle between the incident light and the mirror is 40°, then the angle between the incident light and the reflected light is ( )

A.140° B.50°

C.100° D.40°

Draw reflected rays according to the law of light reflection:

Art style:

1. First find the incident point. The perpendicular line passing through the incident point as the reflecting surface is the normal line. The normal line should be drawn as a dotted line.

2. Find the angle of incidence and measure the angle of incidence.

3. Draw an angle through the incident point and the normal line to make the reflection angle equal to the incident angle.

4. Mark the direction of reflection with an arrow.

Things to note when making optical path diagrams

Standard drawing requirements:

1. You must use a ruler, compass, and pencil for drawing.

2. Use solid lines for light and draw arrows to indicate the direction of light propagation.

3. Draw a dotted line on the normal line

4. A diagonal line should be drawn on the opposite side of the reflective surface

5. Mark the reflection angle r and incident angle i

think

1. Why does the projector screen use rough white cloth?

Parallel light is diffusely reflected on rough surfaces, making it visible in all directions.

2. We can see objects that do not emit light from different directions because light strikes the object and _________ occurs.

Analyze the phenomenon:

(1) Why can we see these non-luminous objects from different directions?

Answer: Generally, the surface of objects is rough. Since parallel light from the sun hits the surface of the object and is diffusely reflected, reflected light reaches the eyes from all directions.

(2) The blackboard is “reflective”

Answer: It’s caused by chalk writing on a smooth blackboard. The chalk characters undergo diffuse reflection and the reflected light intensity of the specular reflection occurs, so the chalk characters cannot be seen clearly.

Knowledge sorting

1. Law of reflection of light:

Incident rays, reflected rays, and normals are on the same plane;

(Three lines are coplanar)

Incident rays and reflected rays are separated on both sides of the normal;

(separation of two lines)

The angle of reflection is equal to the angle of incidence;

(Two angles are equal)

2. Specular reflection and diffuse reflection:

Specular reflection: A beam of parallel light is incident on the surface of an object, and its reflected beam is still parallel. This reflection is called specular reflection.

Diffuse reflection: After parallel light is incident, it is no longer parallel after reflection, but radiates in all directions. This reflection is called diffuse reflection.

(Specular reflection and diffuse reflection both obey the law of light reflection)

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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: 2024-10-04

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

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