seegongsik
Grade 3 (age 8-9)

grade 3 Shadow and Sunlight

When you stand in a playground, your shadow stretches across the ground from your feet. A shadow is the place behind your body that light cannot reach, because light travels in straight lines and your body blocks it. That is why a shadow always falls on the side away from the sun. In the morning and evening, when the sun is low, shadows are long, and at midday, when the sun is high, they get short. In the first picture, change the size of an object and watch its shadow on the screen; in the second, move the sun from east to west and compare the direction and length of the shadow.

How does a shadow form?

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💡 What a shadow needs
①Something that gives off light, such as the sun or a flashlight
②Light travels straight, so when an object blocks it, it cannot bend around behind
③The dark area behind the object that light cannot reach is the shadow
④The dotted lines are light just grazing the top and bottom of the object; the bigger the object, the wider these lines spread and the bigger the shadow

The sun's position and shadows

Midday: sun in the south
☀️ How shadows change during the day
①In the morning the sun is low in the east, so the shadow stretches long to the west
②At midday the sun is high in the southern sky, so the shadow is short and points north
③In the evening the sun is low in the west, so the shadow stretches long to the east
④In Korea the sun never climbs straight overhead, even at midday, so the shadow never disappears completely

What shadows tell us

🎭 What shadows tell us
①Look opposite the way a shadow points and you will find where the sun is
②The length of a shadow tells you roughly how high the sun is
③A sundial is a tool that tells the time from the direction a stick's shadow points
④Even in the same spot on the same day, a shadow swings from west → north → east between morning and evening

Summary

Why shadows form
Light + Object that blocks it = Shadow
A shadow forms behind an object that blocks light travelling in a straight line
Shadow direction
Shadow direction = opposite the sun
When the sun is in the east, the shadow points west
Shadow length
High sun → short shadow / Low sun → long shadow
So shadows are shortest at midday and long in the morning and evening
🎯 Key points
①A shadow forms when an object blocks light that travels in straight lines
②A shadow always falls opposite the sun
③Shadows are short at midday and long in the morning and evening
④During the day a shadow turns from west → north → east
⑤An object that lets light through easily, like glass, casts only a faint shadow

Examples and Unit Test

Example 1
In the morning, when the sun is in the east, which way does the shadow of a friend standing in the playground point?
1
A shadow falls on the side where light is blocked, which is the side opposite the sun.
2
The sun is in the east, so the shadow points to the opposite side, west, and it stretches long because the sun is low.
▸ It points west (opposite the sun) and is long
Move the sun to the far left (east) of the second picture and the shadow stretches far to the right (west).
Example 2
Which is shorter, the shadow at midday or the shadow in the evening, and why?
1
The higher the sun, the more the light shines down from above, and the shorter the shadow.
2
At midday the sun is at its highest, so the shadow is at its shortest, while in the evening the sun is low and the shadow is long.
▸ At midday (because the sun is high)
The words under the second picture show a shadow shorter than your height at midday and several times your height in the morning and evening.
Unit-test style
Which statement about shadows and the sun is correct?
①A shadow forms on the same side as the sun
②A shadow forms on the side opposite the sun
③The higher the sun rises, the longer the shadow gets
④Clear glass makes a dark shadow
⑤A shadow can form even without light
▸ ② A shadow forms on the side opposite the sun
1
A shadow forms behind the object blocking the light, which is the side opposite the sun.
2
A shadow forms opposite the sun (①), the higher the sun the shorter the shadow (③), clear glass lets light through so its shadow is faint (④), and a shadow needs light to form (⑤).
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