Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A shadow is an area of darkness formed when an opaque object blocks light from a source.
Light travels in straight lines. It cannot bend around objects to fill the space behind them.
Transparent materials (like glass) allow light to pass through, so they do not cast a shadow.
Translucent materials (like frosted paper) allow some light to pass through, casting a faint or blurry shadow.
Opaque materials (like wood or metal) block all light, casting a dark, well-defined shadow.
The position of the light source affects the position of the shadow. The shadow is always on the opposite side of the light source.
The size of a shadow changes based on distance. Moving the object closer to the light source makes the shadow larger, while moving it further away makes it smaller.
📐Formulae
💡Examples
Problem 1:
A toy car is placed away from a torch. Its shadow is measured. If the toy car is moved to away from the torch, will the shadow get bigger or smaller?
Solution:
The shadow will get smaller.
Explanation:
When the distance between the light source and the object increases (from to ), the object blocks a smaller angle of light rays, resulting in a smaller shadow on the screen.
Problem 2:
At what time of day will a tree cast the longest shadow: Sunrise, Noon, or Sunset?
Solution:
Sunrise and Sunset.
Explanation:
At Sunrise and Sunset, the Sun is low in the sky (at a sharp angle). Because light travels in straight lines, a low light source creates a very long shadow. At Noon, the Sun is directly overhead, creating the shortest shadow.