Does a shadow grow when the light comes closer?
- 🙅 Never at faces
My hypothesis
If I change how far the flashlight is from the toy, then how long the toy's shadow is on the wall will ______, because ______.
You fill in the blanks. Think about how the light spreads out from the flashlight, and what the toy blocks. A guess is a good because: the test finds out.
Change, measure, keep the same
CHANGE
how far the flashlight is from the toy: 20 cm from the toy, 40 cm from the toy, 60 cm from the toy, 80 cm from the toy
MEASURE
how long the toy's shadow is on the wall, in cm
KEEP THE SAME
- the same toy car, standing in the same spot
- the same distance between the car and the wall
- the same flashlight, aimed at the middle of the car
- the same dim room
Scientists call the thing you change the independent variable and the thing you measure the dependent variable. The things you keep the same are the controls: if one of them changed too, you wouldn't know which change made the difference. Try each of the 4 levels 3 times.
What you need
- A toy car: 1 toy car
- A flashlight
- A tape measure, or a long ruler
- Masking tape, to mark lines
Steps
- Stand the toy car on a table, about 30 cm from a bare wall, with its side facing the wall.
- Stick bits of tape on the table in a line away from the car, at 20, 40, 60 and 80 cm.
- Close the curtains and turn off the lights, so the room is dim.
- Put the front of the flashlight on the 20 cm mark, aim it at the car and switch it on.
- Stick a bit of tape on the wall at each end of the car's shadow.
- Measure from one tape to the other, and write the number in your table under Try 1.
- Move the flashlight to 40, 60 and 80 cm, and measure the shadow each time.
- Do all four distances again for Try 2, then once more for Try 3.
- Find the middle number for each distance and draw a line graph.
Every step is one you can do yourself, with a grown-up nearby. Write each number down straight away, in the table below, so nothing is lost.
Your results table
Name ______________________ Fair day ____________
Question: Does a shadow grow when the light comes closer?
I changed: Flashlight distance I measured: how long the toy's shadow is on the wall (cm)
| Flashlight distance | Try 1 (cm) | Try 2 (cm) | Try 3 (cm) | Mean |
|---|---|---|---|---|
| 20 cm from the toy | ||||
| 40 cm from the toy | ||||
| 60 cm from the toy | ||||
| 80 cm from the toy |
MY GRAPH (a line graph: flashlight distance along the bottom, cm up the side)
What I noticed: ______________________________________________
From 4th grade, add the tries for each level and divide by how many there were: that's the mean, and it goes in the last column. Then draw a line graph, because the thing you change is a number that goes up.
Name ______________________ Fair day ____________
Question: Does a shadow grow when the light comes closer?
If I change how far the flashlight is from the toy, then how long the toy's shadow is on the wall will ________________, because _____________________________________________
| I CHANGE | I MEASURE | I KEEP THE SAME |
|---|---|---|
| Flashlight distance: 20 cm from the toy, 40 cm from the toy, 60 cm from the toy, 80 cm from the toy | how long the toy's shadow is on the wall (cm) |
|
What I think will happen, in my own words:
Name ______________________ Fair day ____________
Question: Does a shadow grow when the light comes closer?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does a shadow grow when the light comes closer?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does a shadow grow when the light comes closer?
| Date | What I did | What I saw | What I think |
|---|---|---|---|
Name ______________________ Fair day ____________
Question: Does a shadow grow when the light comes closer?
My hypothesis was ☐ right ☐ partly right ☐ not right.
I know because my numbers show:
What surprised me, or what might have gone wrong (7th and up):
Next time I would test:
Idea: Change a second thing: keep the flashlight at 40 cm and move the car toward the wall in steps, and graph the shadow's length at each place.
Why it works
Light travels in straight lines and spreads out from the flashlight, and the toy blocks the light that hits it. Close to the toy, the blocked light fans out a long way before it reaches the wall, so the shadow is big. Farther away, the light reaching the toy is closer to parallel, so the shadow is nearer to the toy's own size.
Going further (7th and up): Change a second thing: keep the flashlight at 40 cm and move the car toward the wall in steps, and graph the shadow's length at each place.
Board layout
- ❓ Question (10 × 8 in): Does a shadow grow when the light comes closer?
- 💭 Hypothesis (10 × 9 in): If I change how far the flashlight is from the toy, then how long the toy's shadow is on the wall will ______, because ______.
- 🧺 Materials (10 × 12 in): 4 things: see your list.
- 🪜 Steps (22 × 9 in): 9 steps, three tries at each level.
- 📊 Results (22 × 16 in): Your table (Flashlight distance down the side, tries across) and your line graph.
- ✅ Conclusion (10 × 14 in): My hypothesis was right / partly right / not right. I know because…
Materials to list: A toy car; A flashlight; A tape measure, or a long ruler; Masking tape, to mark lines.
Bring photos or drawings of your test. Nothing wet, hot, powered or alive on the table.
This project at your grade
| 1st–3rd grade | Tries: three at each level (one is fine at a first fair). The table: levels and tries, numbers or pictures. The graph: a picture, or a simple bar graph. The conclusion: what happened, in their words. |
|---|---|
| 4th–6th grade | Tries: three at each level. The table: units in the header and a mean column. The graph: a bar graph, or a line for a number that grows. The conclusion: right, partly or not, and the numbers that show it. |
From 4th grade up, the table gets a mean column. See every project for 1st grade, or print a blank results table.
What a judge will ask
- What did you change, and what did you measure? I changed how far the flashlight is from the toy and measured how long the toy's shadow is on the wall, in cm.
- What did you keep the same, and why does that matter? I kept the same toy car, standing in the same spot and the same distance between the car and the wall the same, so the only difference was how far the flashlight is from the toy.
- How many times did you test it? 3 times at each of my 4 levels.
- If you did it again, what would you change or test next? I'd keep the flashlight at 40 cm and move the car toward the wall in steps, and graph the shadow's length at each place.
Make it yours
Keep this project on this device and Peabody counts down to your fair day, with a plan for each day. Nothing is sent anywhere.
Try next
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