"Propagation of Light" PPT courseware on light phenomena 5

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"Propagation of Light" PPT courseware on light phenomena 5

1. Light source

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

2. Light source classification: natural light source, artificial light source.

Go to life

1. The following objects must not be considered light sources ( )

A. Stars B. Textbooks C. Fireworks D. Beacon light

2. Among light sources such as stars, torches, candlelight fish, and light-emitting diodes, natural light sources include __________, and artificial light sources include __________.

2. How light spreads

(1). Conjecture:

(2). Discussion:

(3) Experiment:

Student group experiments:

Conclusion: Light travels in straight lines in water.

3. Light:

In order to visually represent the propagation of light, we can draw a straight line along the propagation route of light. And draw an arrow on the straight line to indicate the propagation direction of light. This straight line indicating the propagation direction of light is called a light ray.

Parallel rays:

Note: 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. In fact, it does not exist.

Go natural:

Which of the following does not belong to the straight line propagation of light ( )

A. The temperature of the lamp is very high when it shines

B. Use an umbrella to block the sun under the scorching sun

C. The formation of shadow, solar and lunar eclipses

D. Dense woods cannot block the pursuit of "straight" sunlight

Small exercise:

1. It is known that the distance from the sun to the earth is 150 million kilometers. How long does it take for sunlight to reach the earth?

Known: S= 15000 ×107 m, V= 3×108m/s

Solution: given by: t=s/v

=(15000 ×107 m )/(3×108m/s)

=500 seconds

Answer: slightly.

practise:

1. The propagation speed of light in vacuum is ( ) meters/second, combined ( ) kilometers/second, combined ( ) kilometers/hour

2. Try to determine which of the following groups is a light source: ( )

A battery and fireflies B battery and candle flame

C fireflies and the moon D fireflies and candle flames

The sea and the sky are vast:

2. What would the world look like if light did not travel in straight lines? Write a short article.

Tip: For example, when you look at the back of your own head, Zhang San’s glasses will appear on Li Si’s nose, etc.

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Update Time: 2024-09-08

This template belongs to Physics courseware Beijing Normal University eighth grade physics volume one industry PPT template

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