"Dispersion of Light" Light Phenomenon PPT Courseware 2

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"Dispersion of Light" Light Phenomenon PPT Courseware 2

1. Dispersion of light

1. Dispersion of light: White light (sunlight) is decomposed into red, orange, yellow, green, blue, indigo, violet and other colors of light through a prism.

2. White light is a mixture of various colored lights.

3． For example: rainbow

The outside is red

The inside is purple

2. Mixing of colors and lights

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

red + green = yellow

red + blue = magenta

green + blue = cyan

red+green+blue=white

Television and movies are all made based on the three primary colors of light and color.

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.

The physiological effects of ultraviolet rays on the human body

Appropriate exposure to ultraviolet rays helps the body synthesize vitamin D. Vitamin D can promote the body's absorption of calcium, which is beneficial to bone growth and many aspects of physical health.

Excessive ultraviolet radiation is harmful to the human body, causing rough skin and even skin cancer!

The earth is surrounded by a thick atmosphere. Most of the ultraviolet rays in sunlight are absorbed by the ozone layer in the upper atmosphere and cannot reach the ground.

At present, the ozone layer is being damaged by Freon and other substances escaping from air conditioners and refrigerators, and a "hole" has appeared in the ozone layer.

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 color of a color TV is produced by the electron gun in the TV shooting onto the phosphor 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 US-British coalition operations against Iraq, US and British soldiers wore infrared night vision goggles at night to detect 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 certain trademarks can be identified using ________ lights.

1. Color of transparent objects

The color of a transparent object is determined by the colored light it transmits.

Colorless transparent bodies can transmit various colored lights.

Black transparent body does not transmit any colored light.

2. Color of opaque objects

The color of an opaque object is determined by the colored light it reflects.

White can reflect various colors of light.

Black can absorb various colors of light.

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Update Time: 2024-11-20

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

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