Light and shadows — Science, 7–10
Light usually travels in straight lines. When an object blocks it, a shadow appears, and its shape and size can change.
What a shadow is
Light comes from a source such as the Sun, a lamp or a torch. It travels in straight lines until something gets in its way. Behind that object, less light arrives, so we see a darker shape called a shadow.
Why shadows matter
People first used shadows to answer a practical question: where is the Sun, and how long has the day gone on? A stick in the ground made a moving shadow that could mark time. The same idea helps us understand sundials, eclipses and why shade feels cooler.
A torch and a toy
Put a toy 20 centimetres from a wall and shine a torch from 40 centimetres away. The toy blocks some of the light, so a shadow appears on the wall. Move the torch to 20 centimetres from the toy: the shadow becomes larger because the toy blocks a wider part of the light spreading towards the wall.
The common mix-up
A common thought is that an object carries its shadow around like a dark sticker. That seems reasonable because the shadow follows the object when the light stays in the same place. In fact, the shadow is a place where light is blocked, so changing the lamp, object or surface can change it.
Shadows outside school
Architects use light and shadow to make buildings comfortable and bright without too much heat. A sunshade over a window blocks high summer sunlight, while lower winter sunlight may enter. Artists and photographers also use shadows to show shape, distance and direction.
Keep exploring
Other languages
Loading MyLeoNes™…