Curiosity
Why Shadows Change Size
By the end of this course, learners can explain why shadow length changes with the Sun's position and predict how a shadow will change based on the angle of the light source.
Before you enter
A complete interactive classroom, not just a preview.
Start when you are ready to enter this Stage's 11 scenes and explore, respond, and learn as you go.
11
Scenes
22 min
Estimated
Content language: en-US
Why does your shadow stretch and shrink during the day?
What this covers
- straight-line-propagation
- Light travels in straight lines away from a source.
- shadow-formation
- A shadow is the dark area behind an object that blocks light from reaching a surface.
- angle-effect
- The angle at which light strikes an object changes the length of its shadow.
- distant-source
- The Sun is so far away that its light rays are nearly parallel when they reach Earth.
- daily-change
- The Sun's angle above the horizon changes throughout the day, causing shadows to change length.
Common misconceptions
Many people assume
Shadows get longer because the Sun moves farther away from Earth during the day.
Actually
Show that the Sun–Earth distance changes very little in a day; a longer shadow is caused by the lower angle of the Sun relative to the horizon.
Not covered here
- mathematical formulas for shadow length
- atmospheric refraction
- Earth's orbital distance variation
- precession or seasonal tilt details
What you'll be able to do
- Predict whether a shadow will be longer at 4 PM or noon and give a reason.
- Explain that a low Sun angle produces a long shadow.
- Distinguish between changing the distance of a point light source and changing its angle to explain shadow size.
- Apply the angle–shadow relationship to explain why winter shadows are longer than summer shadows, even at noon.
Written for
Curious learners ages 13+ with a basic understanding of day and night but no formal physics background.
What happens inside
- 01A Shadow Mysteryslide
- 02First Guess: Angle or Distance?interactive
- 03Building the Ray Modelinteractive
- 04Angle vs. Distanceinteractive
- 05The Sun's Changing Angleinteractive
- 06Shadow Target Challengeinteractive
- 07Predict and Verifyinteractive
- 08Point vs. Parallelinteractive
- 09Putting It All Togetherslide
- 10Tree Shadow Puzzleinteractive
- 11A New Questionslide
Discussion
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Where this leads
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