"Light and Color" Wonderful Light PPT Courseware 2

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"Light and Color" Wonderful Light PPT Courseware 2

Question: Why can you see the words in the book?

(Because light enters people’s eyes)

Please close your eyes, can you still see these pictures?

Can't Why?

Light does not enter our eyes.

In order for us to see an object, light must enter our eyes from the object.

So where does light come from? Please tell the students what things in life can shine on their own?

We often talk about the bright moonlight. Is the moon a light source? Brilliant diamonds, right? Why?

But we clearly saw the moon and diamonds. Don’t we say that to see an object, light must enter our eyes from the object?

Therefore, the moon, diamonds, tables, and chairs are not sources of light. We can see it because it reflects light, and the reflected light enters our eyes, so we see it.

The following are similar light sources but cannot be called light sources: moon, gems, movie screens, mirrors

A light source refers to an object that emits light and is emitting light. Being able to shine has many meanings. The basic understanding is that it can shine on its own without relying on the outside world. For example, burning matches, electrified lights, turned on TV, sun, lightning, fireflies, lit candles, torches, red-hot iron bars, various neon lights, stars, glowing jellyfish

Can you help sort them?

Natural light sources such as the sun and artificial light sources such as electric lamps

Summary: Development of artificial light sources:

Bonfire—torch—oil lamp—candle—electric light—laser

The development of artificial light sources is the process of human civilization and social development.

What is the propagation route of light? Ask students to design experiments and verify

Use a laser pointer instead of a flashlight

(1) Spread in the air. (Fill an empty glass jar with mosquito-repellent smoke and illuminate it with a laser pointer)

(2) Spread in liquid. (In a basin filled with water, put some chalk dust or milk...)

(3) Spread in glass. (illumination along the surface of a glass block)

Light propagates in straight lines in homogeneous, homogeneous, transparent substances.

Question: In life, we often mention light. Do you know what light refers to in science?

Light: A straight line with an arrow is often used to represent the propagation route and direction of light.

Notice:

Light is a straight line with an arrow drawn by people to visually represent the straight-line propagation of light. It is a method of expressing the propagation of light, but it does not actually exist.

What other examples in life can prove that light propagates in a straight line?

Shadow formation, solar eclipse, lunar eclipse, pinhole imaging, laser collimation, etc.

3. The phenomenon of linear propagation of light

(1) Formation of shadow:

During the propagation process, light encounters an opaque object and creates a shadow behind the object.

think

When aiming and shooting with a rifle, when the eye sees that the aiming point, the front sight tip and the notch coincide, it is considered that the three are in the same straight line. What is the reason for this?

Light propagates along straight lines in the same homogeneous material.

When it thunders, thunder and lightning happen at the same time, but we always see the lightning first and then hear the thunder. What does this mean?

Light travels much faster than sound

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For more information about the "Wonderful Light and Color" PPT courseware, please click on the "Wonderful Light ppt Light and Color ppt" tab.

"Light and Color" wonderful light PPT courseware:

"Light and Color" Wonderful Light PPT Courseware Talk about objects that can emit light in life? Light source: a glowing object. Common light sources in life: the sun, fireflies, bonfires and torches, oil lamps, burning candles, electric lamps, lasers. Propagation of light. Light energy travels in the air..

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Update Time: 2024-09-30

This template belongs to science courseware People's Education Press Fourth Grade Science Volume 2 industry PPT template

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