Light travels in straight lines
Light cannot bend round corners.
Beams of light
When sunlight shines through gaps in clouds or trees, you can see straight beams. Torch and car headlight beams are straight too. This is evidence that light travels in straight lines.
Sunbeams through gaps in clouds are called crepuscular rays. They look as if they spread out, but each beam is a straight line.
The card test
Make holes in three cards and stand them in a row. Shine a torch through the holes. You see the light only when the holes are in a straight line. Move one card and the light is blocked.
This is a simple experiment that anyone can repeat – an important feature of good scientific evidence.
Shadows are evidence
An opaque object blocks light. Because light cannot bend round it, a dark shadow forms behind it. The shadow has the same outline as the object.
If light could bend round objects, there would be no sharp shadows at all.
Light is fast
Light travels at about 300,000 km every second. Nothing in the universe travels faster.
Light takes about 1.3 seconds to travel from the Moon to the Earth and about 8 minutes from the Sun.
What I learnt
- I know that light travels in straight lines.
- I can describe evidence for this.