Light and shadows — Physics, 4–6 years
We see things when light reaches our eyes. An object in the way can block some light and make a shadow.
Light lets us see
A lamp, the Sun, or a candle sends out light. When that light reaches an object and then your eyes, you can see the object. If something stands between the light and a surface, the blocked part can look dark: that is a shadow.
Why shadows appear
People noticed shadows because the dark shapes followed them in sunlight and appeared beside lamps. Shadows answer a useful question: where is light blocked? Looking at one can show the position of an object even when its shape is hard to see.
Make a hand shadow
Stand a torch facing a wall and hold your hand between them. The torch sends light towards the wall, but your hand blocks that part of the light. A dark hand shape appears. Move your hand nearer the torch: the shadow grows larger on the wall.
A shadow is not paint
A shadow can look like a dark thing stuck to the floor, so it is natural to think it is part of the object. It is really a place where light is missing. Move the object or the lamp and the shadow moves or changes shape too.
Finding our way
Light and shadows help us read, walk safely, and find objects in a dim room. A street lamp makes a darker patch behind a fence, and a sundial uses a moving shadow to show the time. Never look straight at the Sun or a very bright lamp.
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