How light travels
Light comes from sources such as the Sun, a lamp, a candle or a torch. When light leaves a source, it moves outwards and lets us see things around us.
An important rule about light is that it travels in a straight line. It does not bend around corners by itself. We can see this when sunlight shines through a small gap and makes a straight beam.
Key idea
Light travels in a straight line. This is why you cannot see around a corner or through a bent pipe.
Shadows show straight light
Because light moves in a straight line, it cannot pass through solid objects. When an object blocks the light, a dark area called a shadow forms behind it.
- Light travels very fast — faster than anything else.
- It needs no air to travel, so it can cross empty space from the Sun to Earth.
Example
Look through three cards with holes lined up in a straight row. You can see a torch only when all three holes are in a straight line.
Remember
- Light always moves in straight lines.
- A shadow forms when light is blocked.