"Propagation of Light" PPT courseware on light phenomena 8

Description

"Propagation of Light" PPT courseware on light phenomena 8

learning target:

1. Know what a light source is and what the two categories of light sources are.

2. Through experimental research, summarize the propagation laws of light and summarize the conditions for straight-line propagation; list application examples of light propagation along straight lines, and be able to use straight-line propagation of light to explain shadow and pinhole imaging phenomena.

3. Remember the propagation speed of light in vacuum and understand that light propagates at different speeds in different media. And can be compared and distinguished with sound.

1. Think about it, why can we see various objects during the day but not in the dark night?

2. What should we do if we want to see objects in the dark night?

[Tracking Exercise 1]

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

A. Polished metal that shines under the sun.

B. Fireflies.

C. The moon.

D. The movie screen when watching a movie

2. Which of the following objects is an artificial light source ( )

A. The sun.

B. Star.

C. Shadowless lamp during surgery.

D. Lantern fish.

[2. How light spreads]

1. Ask a question: After the light source emits light and enters our eyes, how does the light propagate?

2. Observe the above pictures and guess: light is transmitted by _____

3. Design experiments:

1. How light travels in air

2. How does light travel in water

Equipment: matches, incense, empty bottle, laser pointer (dual use of red light and white light), beaker, copper sulfate solution

(1) There should be a light source

(2) How can we see the light path clearly?

4. Conduct experiments - verify conjectures:

Experiment 1: Place the empty bottle upright with its mouth facing down, light a piece of incense, and then insert it into the bottle. When the bottle is filled with smoke, illuminate it with a laser light (red light source) and observe the propagation path of the light.

1. This experiment shows that light propagates along _____ in the air.

Experiment 2: First stir the copper sulfate solution in the beaker (using a ballpoint pen or scale), use a laser light (switching between red and white light sources) to illuminate the blue solution on the upper surface of the water, and observe the propagation path of light in the water from above.

2. This experiment shows that light propagates along _____ in water.

Make a small hole in the bottom of an empty jar, place a lit candle on the left side of the hole, and place a transparent film on the right side of the hole. You can see the image of the candle's flame on the film through the small hole.

Features:

①The nature of the image is ______ (inverted, upright); ______ (virtual image, real image).

②Keep the distance between the candle flame and the small hole unchanged.

As the film moves away from the hole, something like _____ is observed (getting bigger, getting smaller, not changing).

Conclusion: The size of the image is _______ (relevant or irrelevant) to the "distance between the cardboard and the light screen".

③The shape of the image and the shape of the object "candle flame" ______, (same, different);

[Tracking Exercise Three]

1. In order to improve the accuracy of timing, photoelectric timing equipment is used on the tracks of large international competitions. However, due to limited conditions, in general sports meets, the competition starts after the referee at the starting point gives the order, and the referee at the end points times the time with a stopwatch. For accurate timing, it should ( )

A. Start timing when you see smoke, as smoke is easy to see.

B． Start timing when you hear a sound because it is easy to hear.

C. Start timing when you see smoke because the speed of light is faster than the speed of sound.

D． Start timing when you see smoke because light doesn't take time to travel.

2. When light enters a certain transparent liquid from air, its propagation speed will be ( )

A. Increase. B. decrease. C. unchanged. D. It may increase or decrease

[Standard inspection]

1. Which of the following objects is not a light source ( )

A. The lit match B. The lamp in the study room

C. The taillight of the car D. The rearview mirror in the cab of the car

2. When lining up, if you see a classmate in front of you blocking all the people in front of you, the line will be straightened. This can be explained by _______.

3. When sunlight shines vertically on a small square hole, the shape of the light spot on the ground is ( )

A. Round B. Square

C. Irregular D. in strips

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Update Time: 2024-07-28

This template belongs to Physics courseware Lu Jiao edition eighth grade physics volume 1 industry PPT template

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