"Linear Propagation of Light" Light Phenomenon PPT

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"Linear Propagation of Light" Light Phenomenon PPT

Part One: Preview Perception

1. Straight line propagation of light

1. Light source.

Objects that can ________.

2. Regularity.

Light propagates along _________ in the same homogeneous medium.

3. Light.

Use a straight line with ________ to represent the ________ and ________ of light propagation.

4. Phenomenon.

Laser collimation, shadow formation, ____________________, etc.

2. The propagation speed of light

1.Light travels fastest in _________:c=______________.

2. The speed of light propagation in different materials ________: the speed in air is very close to ________, the speed in water is about ________, and the speed in glass is about ________.

Straight line propagation of light PPT, part 2: interactive classroom understanding

propagation of light

1. The propagation of light does not depend on the medium. It can propagate in the medium and in a vacuum.

2. Conditions for light to propagate along a straight line: (1) Light propagates in the same medium; (2) The medium is uniform and transparent. These two conditions must be met at the same time before we can conclude that light propagates in a straight line. If the medium is not uniform, the direction of light propagation in the same medium will be bent; at the interface between two media, the direction of light propagation will also change.

3. Common phenomena: shadow, solar eclipse, lunar eclipse, small hole imaging.

[Example] As shown in the picture, when an annular solar eclipse occurs, the bright spots formed on the ground under the trees through the dense leaves are ()

A. Ring-shaped B. Round

C. Leaf-shaped D. Hole shape

Tip: The principle of pinhole imaging is that light propagates along a straight line in the same uniform medium, and the nature of the imaging is an inverted real image, regardless of the shape of the pinhole.

Analysis: The phenomenon of forming bright spots is a small hole imaging, and the shape of the image is the same as the shape of the light source. Therefore, the sun becomes a donut shape after being partially covered by the moon, and the resulting image is donut-shaped.

Answer:A

Straight line propagation of light PPT, Part 3: Try the application

1. Straight line propagation of light

1. As shown in the figure, the following are not light sources ()

2. Which of the following statements is correct ()

A.Light always travels in straight lines

B. Light always propagates in a straight line in the same medium

C. The image of a plane mirror is formed by the linear propagation of light

D. Light always propagates in straight lines in the same homogeneous medium.

This question examines the conditions for light to propagate along a straight line. If the medium is not uniform, light may not necessarily propagate in a straight line, so choose D.

3. As shown in the figure, when practicing aiming with a rifle, when the eyes see the aiming point, the front sight tip and the notch of the ruler overlapping, it is considered that the three are on the same straight line, and the target can be shot. this means_____.

2. The propagation speed of light

4. No one can run as fast as me! I am ()

A. High-speed maglev train

B. Supersonic fighter jets flying at high altitudes

C. The sunshine that makes all things grow

D. The launch vehicle that sent Tiangong-2 to heaven

5. When there is lightning and thunder, we always see the lightning first and then hear the thunder, which means that the speed of light is _______ (optional "larger" or "smaller") than the speed of sound; the speed of light in vacuum is _______m/s.

When the propagation distance is the same, light propagates quickly, that is, it takes a short time, so the propagation speed of light in the air is greater than that of sound. The speed of light in vacuum is 3×108 m/s.

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Update Time: 2024-10-03

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

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