- Define and explain How Shadows Form in your own words
- Use key terms such as shadow accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on How Shadows Form: seeing how an opaque object blocks light to make a shadow.
Seeing how an opaque object blocks light to make a shadow.
Key ideas
Shadows form when light is blocked
Stand in sunshine and your body blocks the Sun's rays, leaving a dark patch — your shadow — on the ground behind you. Only opaque objects make proper shadows; transparent glass lets the light straight through. The shadow always falls on the opposite side from the light source.
Moving the light or object changes the shadow
Hold a puppet close to a lamp and its shadow on the wall is huge; move it away and the shadow shrinks. Bringing the object nearer the light blocks a wider spread of rays, so the shadow grows. This is how shadow puppet shows make giant characters from small hands.
Key term — shadow: The dark shape formed when an object blocks light from reaching a surface.
At midday your shadow is short; in the evening it is long. Why?
At midday the Sun is high overhead so light comes almost straight down; in the evening the Sun is low, so your body blocks rays at a shallow angle and the shadow stretches out.
Answer: At midday the Sun is high overhead so light comes almost straight down; in the evening the Sun is low, so your body blocks rays at a shallow angle and the shadow stretches out.
- Believing light bends around objects Light travels in straight lines, which is exactly why shadows exist.
- Thinking shadows can appear on the same side as the light A shadow always falls opposite the light source, where the light is blocked.
Practice
Glass is transparent, so light passes straight through instead of being blocked.
The shadow gets smaller, because the toy blocks a narrower spread of rays.
The Sun and stars (also acceptable: lightning, fireflies, glow-worms).
No — a mirror reflects light from a real source; it does not produce light itself.
Quick check
Which of these best defines "shadow"?
Why can't you see someone standing around a corner?
- How Shadows Form: seeing how an opaque object blocks light to make a shadow.
- Shadows form when light is blocked: Stand in sunshine and your body blocks the Sun's rays, leaving a dark patch — your shadow — on the ground behind you.
- opaque: A material that light cannot pass through, so it makes a clear dark shadow.
- Watch out for: believing light bends around objects