Shadows are dark shapes made when an object blocks light. With a flashlight and a few everyday materials, children can investigate how shadows change when the light, object, or screen moves.
What You Need
Gather these materials before you begin:
- A flashlight or torch
- A clear wall, white sheet, or large piece of paper as a screen
- Several small objects with different shapes, such as a toy, spoon, block, leaf, cup, or stuffed animal
- A ruler or measuring tape
- A pencil and paper for recording observations
- Optional: masking tape, a cardboard box, transparent plastic, tracing paper, and colored paper
A bright flashlight with a focused beam usually makes the clearest shadow. A phone flashlight can work, but it may produce a smaller or less even beam. If you use a phone, keep it in a safe place where it will not be dropped or covered by materials.
Choose a dim room so the flashlight beam is easy to see. You do not need complete darkness. A small amount of room light can make it easier to move around safely.
Stay Safe While You Explore
Never shine a flashlight directly into anyone’s eyes. Do not use lasers for shadow experiments, because laser light can damage eyesight. Keep the flashlight away from water, flames, hot surfaces, and loose batteries.
Use a stable table or floor area and remove objects that could cause tripping. If you are exploring in a dark room, have an adult nearby or leave a small light on. Do not stare into the flashlight beam, even if it seems comfortable.
If the flashlight becomes hot, switch it off and let it cool. LED flashlights usually stay cooler, but they can still warm up during long use.
First Investigation: Make a Shadow
Start with a simple shadow test.
- Stand an object between the flashlight and the wall or sheet.
- Point the flashlight toward the object so the beam continues past it to the screen.
- Move the object until a dark shape appears.
- Trace the shadow’s outline on paper, or describe its shape in your notes.
- Label the object and record the approximate distance between the flashlight, object, and screen.
Try the same procedure with several objects. Compare a wooden block, a spoon, a leaf, and a toy figure. Ask:
- Which objects make dark shadows?
- Which objects make faint shadows?
- Does the shadow look like the object?
- Can you identify the object from its shadow alone?
- Which details disappear in the shadow?
A shadow is usually darkest where the object blocks most of the light. A thin object may create a narrow shadow, while a wide object may make a broad one. The outline may be recognizable, but small surface details, colors, and textures often disappear.
Investigate Distance and Shadow Size
The distance between the flashlight, object, and screen has a major effect on the shadow. Keep the screen in one place and use the same object throughout this investigation.
Begin with the object close to the screen. Then move it slowly toward the flashlight. Watch the shadow as you move it.
Record your observations in a table like this:
| Object position | Shadow size | Shadow edge | What changed? |
|---|---|---|---|
| Near the screen | Usually smaller | Often sharper | Shape is close to the object’s outline |
| Between the screen and flashlight | Usually larger | Often softer | The beam spreads around the object |
| Very close to the flashlight | Much larger | May become blurry | Small movements create large changes |
The exact result depends on the flashlight’s design and beam. A narrow, focused beam may produce different results from a wide beam. The important pattern to look for is that an object closer to the light often casts a larger shadow on the screen.
Try placing two objects at different distances from the flashlight. Which object makes the larger shadow? Can a small object make a larger shadow than a bigger object if it is closer to the light?
Change the Direction of the Light
Keep the object and screen in the same places, but point the flashlight from different directions. Shine it from the left, right, above, and below the object.
Each time, predict where the shadow will appear before turning on the flashlight. Then check your prediction. Draw a quick diagram showing the flashlight, object, and shadow.
Try these variations:
- Point the flashlight straight at the object to make a shadow behind it.
- Hold the flashlight low to make a long shadow rising across the wall.
- Hold it high to create a shadow that stretches downward.
- Move the flashlight sideways and observe how the shadow moves in the opposite direction.
The shadow appears on the side away from the light source. This gives you a useful way to think about light direction: if you can see where the shadow falls, you can make a reasonable guess about where the flashlight is located.
Use masking tape to mark the flashlight’s position on the floor. Compare shadows from several positions while keeping the object still. This makes the differences easier to notice.
Explore Shape, Detail, and Materials
Not all objects block light in the same way. Sort your materials into three groups:
- Opaque: Blocks most light, such as a book, block, or metal spoon.
- Translucent: Lets some light through, such as tracing paper or frosted plastic.
- Transparent: Lets much of the light through, such as clear plastic or glass.
Place one item from each group between the flashlight and screen. Compare the shadows.
Opaque materials usually make the darkest, clearest shadows. Translucent materials may make pale shadows with fuzzy details. Transparent materials may create a very faint shadow or mainly show a change in brightness. The result also depends on thickness, color, surface texture, and the angle of the light.
Try a transparent cup, a sheet of colored plastic, and a clear ruler. Look closely at the screen rather than expecting every transparent item to produce no shadow. Edges, thickness, labels, and scratches can block or scatter some light.
You can also investigate cutout shapes. Cut a star, heart, or animal shape from cardboard. Hold it near the screen and then near the flashlight. Does the outline stay the same? Which position gives the sharpest edges?
Make Shadow Puppets
Shadow puppets turn the investigation into a moving experiment. Stretch a white sheet between two chairs, or use a blank wall as the screen. Place the flashlight behind your hands or paper figures and face the shadow toward the screen.
For sharper outlines:
- Keep the puppet close to the screen.
- Hold the flashlight directly behind the puppet.
- Use simple shapes with smooth edges.
- Avoid bright room lights shining toward the screen.
For larger, softer shadows, move the puppet toward the flashlight. Make a rabbit, bird, dog, or imaginary creature with your hands or cardstock. Move one part at a time and observe which feature changes first.
A useful challenge is to make a shadow that looks tall, short, wide, or stretched without changing the object itself. Change only the flashlight’s position or the object’s distance from the screen. Explain which adjustment produced the result.
Build a Simple Shadow Theater
A small cardboard box can become a shadow theater. Remove the front and cut a window from one side. Cover the window with white paper or thin white fabric. Place a flashlight behind the screen and move paper figures between the light and the screen.
Use cardboard strips as handles so you can move the figures without putting your hands in the beam. Test figures made from black paper, white paper, and colored paper. The screen will mainly show their outlines, but a colored filter or translucent paper may change the brightness and color of the light passing through.
Keep the flashlight several centimeters away from paper and never leave it switched on unattended. If the light or paper becomes warm, stop and allow everything to cool.
Record Evidence and Make Predictions
Scientists learn more when they record what happened instead of relying only on memory. Make a simple observation sheet with these headings:
- Object used
- Flashlight position
- Object position
- Screen position
- Shadow size
- Shadow sharpness
- Prediction
- Result
Measure the distance with a ruler when possible. For example, you might place the flashlight 20 centimeters from the object and the screen 60 centimeters behind it. Then repeat the experiment with the flashlight 40 centimeters from the object.
Before each change, write a prediction such as, “If I move the object closer to the flashlight, the shadow will become larger.” After testing, mark the prediction as supported, partly supported, or not supported. If the result is unclear, repeat the test while changing only one distance at a time.
Avoid changing several things together. If you move the flashlight, object, and screen all at once, you will not know which change caused the new shadow.
Troubleshooting Common Problems
The shadow is too faint. Dim the room, use a darker opaque object, move the flashlight closer, or place the object so it blocks more of the beam.
The shadow is blurry. Move the object closer to the screen, steady the flashlight, and use an object with a clear outline. Some flashlights naturally create softer edges.
The shadow disappears. Check that the flashlight is aimed at the object and that the screen is in the beam. Transparent or very thin objects may allow most of the light through.
The shadow is too large for the wall. Move the object closer to the screen or move the flashlight farther away, if the beam still reaches the object clearly.
The result changes each time. Mark positions with tape, use a stable stand or stack of books, and change only one variable. Check for daylight or other lamps that may be adding extra shadows.
The outline looks distorted. The object may be tilted, or the flashlight may be shining at an angle. Rotate the object and compare the outline from different directions.
Further Challenges
Try these additional questions:
- Can you create two shadows from one object using two flashlights?
- What happens when two objects overlap?
- Can you make a shadow larger without moving the screen?
- Does a crumpled object make a different shadow from the same object when it is flat?
- Can you identify an object using only its shadow?
- Which household object makes the most unusual silhouette?
- How does a shadow change when the flashlight is moved in a circle around the object?
Remember that shadows are not always perfectly sharp or completely black. Flashlight brightness, beam width, object thickness, screen color, room lighting, and distance all affect the result. These limitations are useful clues: they show that a shadow depends on the entire arrangement of light, object, and surface, not just on the object by itself.