"Exploring the Law of Reflection of Light" Light and Eyes PPT Courseware 2

"Exploring the Law of Reflection of Light" Light and Eyes PPT Courseware 2

learning target

1. Know what the reflection of light is

2. Understand the law of reflection of light and the reversibility of light path in reflection phenomenon

3. Know specular reflection and diffuse reflection, and be able to use them to analyze some simple phenomena

Core test points: the law of reflection of light, simple optical drawing.

Preview before class

1. Reflection: The phenomenon that light changes _________ at the interface between two media and then returns to the original medium is called reflection of light.

2. The law of reflection of light: When light is reflected, ________, ________ and ________ are in the same plane, and the reflected light and incident light are located on both sides of ________ respectively.

. Angle ________ is equal to angle ________.

3. Specular reflection and diffuse reflection: Specular reflection is the reflection of light when it hits the ________ surface, while diffuse reflection is the reflection of light when it hits the ________ surface. Both types of reflection are ________ reflections of light. law.

4. In the reflection phenomenon, if the light is directed toward the mirror in the direction of the reflected light, it can be seen that the reflected light will be directed in the direction of the original incident light, which indicates that during reflection, ________.

5. Which of the following statements violates the law of light reflection ( )

A. When the incident angle increases by 10°, the reflection angle also increases by 10°

B． When the incident angle is 0°, the reflection angle is also 0°

C. The direction of the incident light does not change, the direction of the normal does not change, and the direction of the reflected light may change.

D． The angle between the incident light and the reflected light is 30°, and the angle between the reflected light and the mirror is 75°

Lectures in class

Knowledge point 1. Reflection of light

(1) Reflection phenomenon of light:

When light hits the surface of an object (or the interface between two media), part of the light returns to the original medium and continues to propagate. The light changes its original propagation direction. This phenomenon is called reflection of light, as shown in the figure below. All The surface of an object can reflect light, and the surface of an object is called a reflective surface. Reflection of light is a ubiquitous phenomenon. We can see objects that do not emit light themselves because the light reflected from their surfaces enters our eyes. .In the phenomenon of light reflection, each ray of light follows the law of light reflection.

[Example 1] Which of the following phenomena belongs to the reflection of light ( )

A. Human shadow B. The back of a person C. shade d. annular solar eclipse

[Exercise 1] (2014•Xiamen) The picture shown is a cartoon by Feng Zikai, with the poem "Planting peaches near water to know the meaning, one plant is regarded as two plants". The optical phenomenon presented in it is ( )

A. Straight line propagation of light B. reflection of light

C. Refraction of light D. dispersion of light

Knowledge point 2. Law of reflection of light

(1) The law of reflection is the only law that can determine the propagation direction of reflected light. To master it, we must first clarify the provisions of "three lines and two angles".

Third line:

Incident light: light that hits the reflective surface, such as AO in the figure below.

Normal: a straight line that passes through the incident point O and is perpendicular to the reflecting surface. It is an auxiliary line, usually represented by a dotted line, such as ON in the figure below.

Reflected light: After the incident light hits the reflective surface, the light is reflected by the reflective surface, such as OB in the figure below.

Two corners:

Incident angle: The angle between the incident ray and the normal, such as .

Reflection angle: The angle between the reflected light and the normal, such as .

Pay special attention to: the two angles are the angles between the two rays and the normal, not the angle between the interface.

(2) Contents of the law of reflection of light: (a) The reflected ray, the incident ray and the normal are in the same plane, and the reflected ray and the incident ray are separated on both sides of the normal; (b) The reflection angle is equal to the incident angle; (c) Reflection The light path in the phenomenon is reversible.

That is, "three lines share one surface; the normal line is in the middle" (three-line relationship); "two angles are equal" (two-angle relationship).

Knowledge point 4. Application of light reflection

(1) Light reflection is not only widely used in life, but also often used in many high and new technologies. For example: ruby ​​lasers use the reflection of light to form strong laser beams; optical fibers use the reflection of light to transmit; artificial satellites use the reflection of light to sense mineral deposits and forests on the ground to estimate crop yields...

(2) Light reflection sometimes affects people's lives. For example, many buildings in modern cities use glass curtain walls, which can easily cause light pollution.

[Example 4] People like a bright environment, but sometimes time can damage people's vision and physical and mental health, causing light pollution. Among the following phenomena, which can cause light pollution are ( )

A. Black glass for car window glass

B． Installing glass curtain walls on large areas of urban buildings

C. Use an eye protection desk lamp when studying at night

D． Use plastic film to build a greenhouse

[Exercise 4] (2014·Deyang) Among the following optical instruments, the one that uses the principle of light reflection is ( )

A. Plane mirror b. Reading glasses C. camera d. nearsighted glasses

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"Exploring the Law of Reflection of Light" Light and Eyes PPT Courseware:

"Exploring the Law of Reflection of Light" Light and Eyes PPT Courseware Teaching Objectives 1. Know what the reflection phenomenon of light is; understand the law of reflection of light, and be able to apply the law of reflection of light to solve some simple problems. Know that in the phenomenon of reflection, the light path is reversible. 2. Know...