seegongsik
Grade 2 (age 7-8)

grade 2 Light & Shadow

Light travels in straight lines, like the beam of a flashlight. So when an object blocks light, the area behind it that the light cannot reach becomes dark, and that is a shadow. In the morning and evening, when the Sun is low, shadows stretch long; at midday, when the Sun is high, they become short. Change the Sun's height in the picture and the shadow grows or shrinks to where the ray passing the treetop reaches the ground.

Why do shadows form?

45°
💡 Light and shadows
①Light travels in straight lines
②When an object blocks light, the area behind it that the light cannot reach is dark
③That dark area is a shadow, and it always falls on the side away from the Sun
④The dotted line in the picture is the light that just grazes the treetop; where it hits the ground is the end of the shadow

Sun height and shadows

🌞 Shadows change with the Sun's height
①In the morning the Sun is low, so shadows are long
②At midday the Sun is high, so shadows are shortest
③In the evening the Sun is low again, so shadows grow long
④When the Sun is 45° high, the shadow is as long as the tree is tall

How light behaves

🔦 Light goes straight
①Turn on a flashlight and the light shoots out straight
②Light cannot bend around behind an object, so a shadow forms
③Make shapes with your hands in front of a light and you can play shadow games on the wall
🌈 Colors hidden in sunlight
①Sunlight looks white, but it is a mix of light of many colors
②After rain, water drops in the air split sunlight into its colors and a rainbow appears
③In a rainbow you see red, orange, yellow, green, blue, indigo and violet in order

Summary

🎯 Light and shadows in short
①Light travels in straight lines
②When an object blocks light, a shadow forms on the side away from the Sun
③In the morning and evening, when the Sun is low, shadows are long
④At midday, when the Sun is high, shadows are short
⑤Sunlight is a mix of light of many colors

Examples and Unit Test

Example 1
Why do shadows form? How does light travel?
1
Light travels straight ahead.
2
When an object blocks the light, a dark area forms behind it: that is the shadow.
▸ Light travels straight, and when an object blocks it, a shadow forms
As the dotted line in the picture shows, light travels straight, so a shadow forms behind the tree.
Example 2
How does a shadow's length change when the Sun is low and when it is high?
1
When the Sun is low, the shadow stretches long.
2
When the Sun is high, the shadow becomes short.
▸ A low Sun makes a long shadow, and a high Sun makes a short one
Set the Sun's height to 15° and then 85° in the picture to see how much the shadow's length changes.
Unit Test
When is a shadow longest?
①When the light shines from low down
②When the light shines from high up
③When there is no light
④When the object is transparent
⑤When the object is small
▸ ① When the light shines from low down
1
When light shines from low down, the shadow stretches long.
2
When light shines from high up, the shadow gets shorter, so shadows are shortest at midday.
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