"Shadow in the Sun" Light PPT

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"Shadow in the Sun" Light PPT

Part One: Observe the changes in shadows of objects under sunlight

Let's verify our ideas with actual observations.

Find a pencil (or a chopstick) about 10 cm long, a smooth board, and a piece of white paper the same size as the board. Glue the white paper to the wooden board, and then fix the pencil vertically on the wooden board with plasticine to make a simple heliostat.

Place the completed heliostat in a place on campus where the sun can always shine.

First look at the direction of the sun, measure the length of the pencil's shadow, and then trace the pencil's shadow with a pen on the white paper.

Observe and record every 10 minutes in class.

Continue to observe after class, observe once every other class, and record the position and direction of the sun and the length of the pencil shadow.

Shadows in the Sun PPT, Part 2: Organizing our records

How do the shadows of objects under sunlight change throughout the day? When is the shadow the longest and when is the shadow the shortest?

The direction of the shadow of an object under sunlight during the day

It changes with the direction of the sun, and the shadow is always in the opposite direction of the sun.

The length of the shadow of an object under sunlight during the day

It changes with the position of the sun in the sky. When the sun is at its highest position, the shadow is shortest, and when the sun is at its lowest position, the shadow is longest.

ancient sun clock dial

Before humans invented mechanical clocks. An ancient solar clock - a sundial - was used to keep time. As the sun's position in the sky continues to change, the shadows of objects on the ground also change accordingly. Sundials are made using this rule.

The earliest extant sundial is the equatorial sundial from the Qin and Han Dynasties (unearthed in Hohhot, Inner Mongolia Autonomous Region in 1897 and now in the Chinese History Museum). As early as the Sui Dynasty, China had written records of sundials.

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Update Time: 2024-09-25

This template belongs to science courseware Fifth Grade Science Volume 1, Textbook Edition industry PPT template

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