"Dispersion of Light" PPT courseware on light phenomena

Description

"Dispersion of Light" PPT courseware on light phenomena

Consolidate and think

[Dispersion Demonstration Experiment] Let a beam of sunlight shine on a prism. What happens to the light emerging from the prism?

Laws of refraction of light:

① When light is refracted, the refracted ray, incident ray and normal line are in the same plane;

②The refracted ray and incident ray are located on both sides of the normal;

③The refraction angle changes with the change of the incident angle: when the incident angle increases, the refraction angle also increases; when the incident angle decreases, the refraction angle also decreases.

Two-corner relationship:

When light is incident obliquely from air into a transparent substance such as water or glass, the angle of refraction is smaller than the angle of incidence;

When light is incident obliquely into air from a transparent substance such as water or glass, the angle of refraction is greater than the angle of incidence.

1. Dispersion of light

Phenomenon: Sunlight (white light) is decomposed into seven colors of light after passing through a prism, which are red, orange, yellow, green, blue, indigo, and violet.

Concept: After passing through a prism, sunlight is decomposed into light of various colors. This phenomenon is called dispersion of light. (notes)

[Conclusion] Sunlight (white light) is a mixture of seven monochromatic lights: red, orange, yellow, green, blue, indigo, and violet. (notes)

Understand monochromatic light and polychromatic light

Monochromatic light: Light that cannot be decomposed after passing through a prism.

Complex color light: It is composed of light of various colors.

2. Mixing of colors and lights

1. The three primary colors of light: red, green, and blue

Mixed in equal proportions into white light

How are the colors in color TVs produced?

The color of the TV picture is composed of three color bars: red, green and blue.

3. Invisible light

1. solar spectrum

The spectrum is formed by decomposing sunlight into different colors of light and arranging them in the order of red, orange, yellow, green, blue, indigo and violet.

Invisible light beyond red light on the spectrum is called infrared, and invisible light beyond violet is called ultraviolet light.

2.Infrared ray

Invisible light other than red light on the spectrum is called infrared light. Although it cannot be seen by the human eye, its existence can be detected with a sensitive thermometer. It is invisible light.

(1) Characteristics of infrared:

① Infrared rays have a thermal effect and can heat the irradiated object;

②The heat of the sun is mainly transmitted to the earth in the form of infrared radiation;

③Objects can absorb infrared rays and also radiate infrared rays.

(2) Application of infrared:

①Infrared heating

②Infrared remote control

③Infrared imaging

3． UV rays

(1) Characteristics and applications of ultraviolet light

①The most significant feature of ultraviolet light is that it can make fluorescent substances glow.

②Ultraviolet disinfection and sterilization

(2) UV protection

Excessive ultraviolet rays can burn the skin and even cause cancer, affecting the survival of animals, plants, and humans.

Mountaineers have to wear special black glasses, and people hold up parasols in the hot summer. Why is this?

summary

1. White light is a mixture of red, orange, yellow, green, blue, indigo, violet and other colors of light.

2. The three primary colors of light: red, green, and blue

3． Characteristics and practical applications of infrared: body temperature measurement, night vision, heating, etc.

4. Characteristics of ultraviolet light, practical applications and hazards: fluorescence effect, banknote inspection, sterilization and disinfection, etc.

Consolidation exercises

1. After sunlight passes through a prism, it will be decomposed into light of various colors. If a white screen is used to receive it, the order of colors on the white screen is red, _____, _____, ______, ______, ______, _____. this means_______________.

2. The colors of color TVs are produced by the electron guns in the TV shooting onto the phosphors on the inside of the screen. According to the mixing rules of color light, only three colors of electron guns, _____, _____, and _______, are needed in the TV. Can be matched with a variety of brilliant colors. Red, green, and blue are called ___________ of light.

3. In the recent U.S. and British coalition operations against Iraq, U.S. and British soldiers wore infrared night vision goggles at night, which allowed them to spot the enemy even in the dark night. Infrared night vision goggles are made based on the principle that the _______ of people at night is _______ than the temperature of surrounding vegetation or buildings, and the _______ of human body radiation is _______.

4. Ultraviolet rays are also invisible light that can cause fluorescent substances to ____. Appropriate ultraviolet rays help the human body synthesize vitamin D. Excessive ultraviolet rays ____ the human body.

5. The anti-counterfeiting marks of RMB and some trademarks can be identified with ________ lights.

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Update Time: 2024-08-22

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

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