How light travels
I can use the idea that light travels in straight lines to explain how we see and why shadows match objects.
For grown-ups: this lesson in words
Year 6 · Science
How light travels: I can use the idea that light travels in straight lines to explain how we see and why shadows match objects.
Here is a torch. It is a light source: it gives out its own light.
Next come three cards, each with a hole. The holes are lined up in one straight row.
Light from the torch passes through all three holes and reaches the eye, so the eye sees the torch.
Light travels in straight lines, so it goes straight through the lined-up holes.
Picture: A sequence called Light through three cards with 5 stages, in order: Torch, then Hole in card 1 (a picture of a sheet of paper), then Hole in card 2 (a picture of a sheet of paper), then Hole in card 3 (a picture of a sheet of paper), then Eye.
Light travels in straight lines. It cannot bend round things.
With all three holes in line, the eye sees the torch. With the middle card moved aside, the card blocks the light.
A torch straight in front can be seen. A torch round a corner cannot, because light cannot bend round the corner.
Picture: Sorting into 2 groups: Eye sees the torch, Eye cannot see the torch. Eye sees the torch: All three holes in line (sheet of paper), Torch straight in front (torch). Eye cannot see the torch: Middle card moved aside (sheet of paper), Torch round a corner (torch).
Your turn: Jonah holds a long, bendy tube straight and looks through it at a lamp. He can see the lamp. Then he bends the tube in the middle. Can he still see the lamp through it?
Choose one:
- Yes. The light follows the bend in the tube.
- Yes, and the lamp looks brighter.
- No. The bend blocks the light, which travels straight.
Answer
The answer: No. The bend blocks the light, which travels straight.
No. With the tube bent, there is no straight path from the lamp to his eye, so the light is blocked.