🔦 Light, Shadows & Optics: Chasing Light and Shadows
Discover how light travels, why shadows form, and how light bounces and bends in this fun Grade 5 science lesson on optics.
Learning Goals
By the end of this lesson, you will be able to:
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Explain how light travels in straight lines
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Describe how and why shadows are formed
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Identify how light reflects off and passes through objects
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Classify objects as transparent, translucent, or opaque
Before You Start
Before this lesson, you should know:
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You should know that the Sun, lamps, and flashlights give off light
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You should be able to tell the difference between day and night
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You should know what a mirror is and what it does
A little background will help you shine in this lesson! ☀️
Key Words
Important words to know for this lesson:
Light Source
Something that makes its own light, like the Sun, a candle, or a flashlight.
Shadow
A dark area made when an object blocks light from passing through.
Reflection
When light bounces off a surface, like a mirror or still water.
Transparent
A material that lets almost all light pass through, like clear glass.
Opaque
A material that blocks light completely, so you can't see through it.
How Light Works
Light is a form of energy that travels in straight lines from a light source and lets us see the world around us.
Light Travels Straight: Light always moves in straight paths called rays. That's why you can't see around corners!
Shadows Form: When an object blocks light, it leaves a dark shape behind it called a shadow. Bigger blocks or closer lights make bigger shadows.
Light Reflects: When light hits a smooth, shiny surface like a mirror, it bounces back and lets us see our reflection.
Materials Matter: Transparent things let light through, translucent things let some through, and opaque things block it all.
Example
When you stand outside on a sunny day, your body blocks the Sun's straight light rays. The light can't pass through you, so a dark shadow of your shape appears on the ground behind you. 🌞
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This diagram shows light rays traveling straight, hitting an object, and creating a shadow behind it.
Let's Try It Together!
Basic
A flashlight shines on a toy that is 10 cm tall. The shadow on the wall is 30 cm tall. How many times taller is the shadow than the toy?
Let's Try a Harder One!
Intermediate
At noon a 150 cm tall student casts a shadow of 50 cm. Later, the shadow grows to 200 cm. How many centimeters longer did the shadow become?
Your Turn to Practice
Try this one yourself — use the hint if you get stuck:
A ball is 8 cm wide. When a lamp shines on it, the shadow is 24 cm wide. How many times wider is the shadow than the ball?
In the Real World
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Sundials tell time using the shadow cast by the sun as it moves across the sky.
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Cameras use lenses to bend light and focus a sharp picture, just like your eye does.
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A solar eclipse happens when the Moon's shadow falls on Earth, blocking the Sun's light.
Quick Check
Test your understanding — tap an answer to check:
Q1.A shadow forms when light is blocked by a(n):
Q2.When does your shadow look longest?
Q3.Light travels in:
Challenge Question
Optional
Stretch your brain — this one's a bit harder!
A flagpole is 2 meters tall and casts a shadow 3 meters long. At the same time, a tree casts a shadow 9 meters long. How tall is the tree?
Key Takeaways
1.Light travels in straight lines until it hits an object.
2.Shadows form when opaque objects block light — the shadow shows the object's shape.
3.The size and direction of a shadow change as the light source moves.
4.Lenses and mirrors bend or bounce light, which is how cameras, eyes, and telescopes work.
Printable Cutouts
Matched to this lesson — untick anything you don't need, then print.
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Ready to Practice?
Now that you've learned Light, Shadows & Optics, put it to the test with a quick quiz!