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Light Helps Us See, and Things Make Shadows · We need light to see, and a shadow appears when an object blocks the light. · 1-PS4-3

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Light Helps Us See, and Things Make Shadows

with Lumi

Lumi the friendly glowing firefly hovers by a sunny window, shining warm light on a toy block that casts a dark shadow on the floor.

Explain that we need light to see things.
Identify that a shadow is a dark shape made when an object blocks light.
Predict where a shadow appears when light shines on an object.

Key terms

shadow: the dark shape made when an object blocks light
block: to stop light from passing through
solid: a hard object that light cannot pass through
straight line: a path that does not bend or curve
light source: anything that makes light, like a lamp or the sun

Light Travels in Straight Lines

Light does not bend around corners on its own — it zooms forward in straight lines. That is why you can shine a flashlight beam across a room and it lands in one bright spot. Because light goes straight, anything solid that gets in the way will stop the beam from reaching the wall behind it.

How a Shadow Is Made

When light traveling in a straight line hits a solid object, the object blocks the light. The light cannot pass through, so the space right behind the object stays dark. That dark space is the shadow, and it has the same shape as the object that blocked the light. Move the object and the shadow moves with it.

Worked examples

Lumi shines a lamp at a wooden block. Where will the shadow appear?

The light travels in a straight line from the lamp toward the block.
The solid block blocks the light so it cannot pass through.
The dark shadow appears on the far side of the block, away from the lamp.

Answer: The shadow appears behind the block, on the side away from the lamp.

Hi! I am Lumi. I make light. Light helps your eyes see! When the room is dark, you cannot see your toys. When the light turns on, you can see them. Your eyes need light to see. Light travels in a straight line. It zooms forward! When light hits a solid object — like a block or a hand — the light cannot go through. The light is blocked. Behind the blocked object, there is no light. That dark shape is called a shadow. A shadow is the same shape as the object that blocks the light. Move your hand in front of a lamp and look at the wall behind it. See the dark hand shape? That is your shadow! Move your hand and the shadow moves too. If you take your hand away, the light is not blocked and the shadow goes away. Not sure yet? Try this: hold your hand up in front of any light — a lamp, a window, even a phone screen. Look for the dark shape behind your hand. That dark shape is your answer!

Activity

Lumi shines light at each object. Pick the things that will block the light and make a shadow.

Practice

Will a solid teddy bear make a shadow when light shines on it?

Move your hand in front of a lamp and watch the shadow move.

Common mistakes to avoid

Brighter light all by itself makes a shadow.A shadow only appears when a solid object blocks the light, not just because the light is bright.
Shadows can appear without anything blocking light.There must be a solid object in the way of the light for a shadow to form.

Check your understanding

Why can you see your toys when the light is on?

What makes a shadow appear?

What happens when you turn off all the lights in a room?

Recap

Light travels in straight lines, and our eyes need it to see. When a solid object blocks the light, the dark space behind it is called a shadow. The shadow is the same shape as the object and moves whenever the object moves.

Reflect

Where have you seen your own shadow before?