Grade 3 (age 8-9)

Shadow and Sunlight

A shadow appears behind an object when light cannot pass through it. So a shadow always falls opposite the sun, long in the morning and evening and short at midday when the sun is high. Long ago people built sundials that told the time from these moving shadows. Here you can change the object size and the sun's position and watch the shadow's direction and length change.

How are shadows made?

Object Size50

💡 For a shadow to form

①You need light (sun, lamp)

②You need an object blocking the light

③If light cannot pass, a shadow forms

④Transparent objects barely cast shadows

Sun and Shadow Relationship

Sun Position90°

☀️ Changes Throughout the Day

①Morning: sun east → shadow west (long)

②Noon: sun high south → shadow north (short)

③Evening: sun west → shadow east (long)

④Shadow always opposite to the sun

Shadow Play

🎭 What Shadows Tell Us

①Shadow direction reveals sun's position

②Sundials use shadows to tell time

③Shadow shape depends on object shape

④Same object, different light direction = different shadow

Summary

Shadow Principle

Light + opaque object = Shadow

When light cannot pass through, a shadow forms behind

Shadow Direction

Shadow direction = opposite of sun

If sun is east, shadow is west

Shadow Length

High sun → short shadow

Low sun → long shadow

🎯 Key Points

①Shadows form when light is blocked

②Shadows fall opposite to the sun

③Short at noon, long at morning/evening

④Sundials use this principle

⑤Transparent objects barely cast shadows

Examples and Unit Test

Example 1

In the morning, when the Sun is in the east, on which side does the shadow of an object form?

A shadow always forms on the opposite side from the Sun.

When the Sun is in the east, the shadow forms on the opposite side, the west.

▸ The west (opposite the Sun)

A shadow always forms on the opposite side from the Sun.

Example 2

Between around noon and the evening, when is the shadow shorter, and why?

The higher the Sun is in the sky, the shorter the shadow becomes.

Around noon the Sun is highest so the shadow is shortest, while in the evening the Sun is low so the shadow is long.

▸ Around noon (the Sun is high, so the shadow is short)

A high Sun makes a short shadow; a low Sun makes a long one.

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 opposite side from the Sun

③The higher the Sun rises, the longer the shadow

④A clear object makes a dark shadow

⑤A shadow forms even without light

▸ ② A shadow forms on the opposite side from the Sun

A shadow forms behind the object that blocks the light, on the side opposite the Sun.

A shadow forms opposite the Sun (①), a higher Sun makes a shorter shadow (③), a clear object barely makes a shadow (④), and a shadow needs light to form (⑤).

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