"Linear Propagation of Light" Light Phenomenon PPT Courseware 8

Description

"Linear Propagation of Light" Light Phenomenon PPT Courseware 8

teaching objectives:

1. Be able to identify light sources. Know that light sources can be roughly divided into natural light sources and artificial light sources.

2. Understand the linear propagation of light and be able to list the applications of linear propagation of light in life.

3. Know the speed of light in vacuum.

4. By observing experiments of light propagating in media, understanding experiments is an important method for studying physical problems.

1. Light source

To study the phenomenon of linear propagation of light, we must first look at which objects can emit light and who brings us light.

Question: What luminous objects have you seen?

summary:

1. Light source: An object that can emit light is called a light source.

For example: sun, stars, fireflies, candles, energy-saving lamps, etc.

2·Classification ①Natural light source ②Artificial light source

2. Propagation of light

1·How does light spread?

Conduct experiments to observe phenomena:

1. How does light travel through the air? ——Propagate in a straight line

2. How does light travel in water? ——Propagate in a straight line

3． How does light travel in glass? ——Propagate in a straight line

2. linear propagation of light

①·The formation of shadow.

Light propagates along straight lines. When light encounters opaque objects during propagation, a dark area is formed behind the object, which is a shadow.

Thinking: How does the length of the tree’s shadow change as the sun moves from east to west?

②·Small hole imaging.

In a dark room, place a lit candle in front of a piece of translucent plastic film, and place a piece of cardboard with holes drilled between them. An inverted image of the candle flame will appear on the plastic film. This kind of The phenomenon is called pinhole imaging.

③·The formation of solar and lunar eclipses.

When the sun's light travels in a straight line, it encounters the opaque moon, and a solar eclipse occurs in the area behind the moon where light cannot reach.

When the sun's light travels in a straight line, it encounters the opaque earth, and a lunar eclipse occurs in the area behind the earth where light cannot reach.

Summary: What did you gain?

1. Light source:

1. An object that can emit light itself is called a light source.

2·Classification: ①Natural light source ②Artificial light source

2. Propagation of light

1·Light propagates along straight lines in the same homogeneous medium.

2. The phenomenon of linear propagation of light

①·The formation of shadow. ②·Small hole imaging. ③·The formation of solar and lunar eclipses.

3. Application of light propagating along straight lines.

4. Light: Usually a straight line with an arrow is used to represent the path and direction of light propagation. Such a straight line is called a light.

3. Speed ​​of light: c= 3×108 meters/second

4. Light-year is a unit of length. One light year = 9.4608×1015 meters

practise:

1. Which of the following objects is a light source ( )

A. Mirror

B. Fireflies

C. The stars at night

D. Polished metal that shines under the sun

2. "One leaf blocks the eye, and one cannot see the mountain." This can be explained by the fact that light propagates in a straight line in a uniform medium.

3. Which of the following statements is correct ( )

A. Light travels in straight lines in any medium.

B. The light emitted by the sun travels in a straight line when it hits the earth.

C. Pinhole imaging shows that light propagates in a straight line in a uniform medium.

D. The speed of light in water is greater than the speed of light in vacuum.

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Update Time: 2024-10-19

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

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