"Linear Propagation of Light" Light Phenomenon PPT Courseware 2

Description

"Linear Propagation of Light" Light Phenomenon PPT Courseware 2

magical light phenomenon

Objects that can emit light are called light sources

natural light source

1 huge fireball sun

2. The active night light——Fireworm

3 Colloidal substance - jellyfish

4 Ocean fish – lantern fish

artificial light

1 candle

2 oil lamps

3 neon lights

4 incandescent lamps

5 lasers

2. How light spreads:

Does light always travel in straight lines?

Experiment 1: Observe the propagation path of laser light in the air

Experiment 2: The laser beam hits the plane mirror and the reflection phenomenon is observed.

Experiment 3: The laser beam is shot on the glass brick and the refraction phenomenon is observed.

Experiment 4: The trajectory of the laser hitting the same inhomogeneous medium.

Conclusion: Light propagates along straight lines in the same homogeneous medium, and light is reflected and refracted at the interface between the two media.

3. Application of linear propagation of light

(1) Team alignment: "Align to the right!"

(2) Small hole imaging

The light passing through the woods will form a "spot" of the sun on the ground - an image of the sun.

(3) Formation of shadow

speed of light

1 The light from the sun takes about 8 minutes to reach the earth.

2 The speed of light in air is slightly smaller than the speed in vacuum.

3 The speed of light in water is about 3/4 of the speed in vacuum.

4 The speed of light in glass is about 2/3 of the speed in vacuum.

practise

1. When the weather is fine, you often see some bright small spots on the ground under the shade of trees. This is caused by light ___________. These spots are ___ shaped and are caused by ______ passing through the gaps in the leaves. Successful ____.

2. In some of the following life scenes, the characteristics of light propagating in straight lines in the same homogeneous medium are used ( )

A. "Hide from the sun" in the shade of trees B. Use a magnifying glass to observe small objects

C. Dressing in front of a flat mirror D. Standing on the shore and watching the fish in the water

3. Which of the following are light sources ( )

A.Sun B.Earth C.Moon D.House

4. The propagation speed of light in a vacuum is ________; among the sun, moon, and fireflies, the ones that are not light sources are ______; please give an example that illustrates the propagation of light in a straight line: _______________.

Summary: The speed of light

1. The fastest light in vacuum is C=3×108m/s

2. The speed of light in air is approximately less than the speed in vacuum. Therefore, we use 3×108m/s in our calculations.

3. The speed of light in other transparent media is smaller.

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"Linear Propagation of Light" Light Phenomenon PPT Courseware 6 1. Light source 1. Light source: An object that can emit light is called a light source. 2. Light sources are divided into two categories: natural light sources and artificial light sources. Natural light sources: stars (such as the sun), fireflies, luminous jellyfish, etc. Artificial light source: electric...

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Update Time: 2024-11-24

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

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