Year 6 Science: Light travels in straight lines
Part of the Year 6 Science light travels in straight lines chapter. Chapter overview · whole chapter on one page
Light travels in straight lines
Light appears to travel in straight lines. We can show this with a torch and cards with holes in them. When the holes are in a straight line, the light passes through them all. If one hole is moved to the side, the light is blocked.
A straight line of light is often drawn as a ray, with an arrow to show the direction the light is travelling.
Key ideas
- Light appears to travel in straight lines.
- A straight line of light is shown as a ray, with an arrow for direction.
- If the holes are not in a straight line, the light is blocked.
- Opaque materials block light; transparent materials let light through.
Method. Look at the holes.
- Read the picture. The holes are all in one straight line with the torch and the wall.in a line
- Decide. So the light passes through all three holes and reaches the wall.yes
- Write the answer. yes
Check. Light travels in straight lines, so it can pass through aligned holes. ✓
Method. Look at the picture with the moved hole.
- Read the picture. The middle hole is moved, so it is not in line with the torch and the wall.not in line
- Decide. The light is blocked by the middle card, so the answer is no.no
- Write the answer. no
Check. Light cannot bend round a card to reach the wall. ✓
Method. Read the description.
- Read the description. A straight line of light, with an arrow for its direction, is a ray.ray
- Check the parts. The straight line shows the path, and the arrow shows which way the light travels.path and direction
- Write the answer. ray
Check. Rays are used in diagrams of light. ✓
Watch out
Watch out: light does not bend round corners in a straight-line model. If an object is in the way, the light is blocked and a shadow forms.
Exam tip
Exam tip. When you use the straight-line idea, say that the light travels in a straight line from the source to the object or the eye.
Try it (with your teacher, or a grown-up at home). Make three cards with a hole in each, and line the holes up. Hold them in front of a torch, with a grown-up. Move one card slightly. What happens to the light? Keep the torch pointed away from people's eyes.
Exercise 7A Light travels in straight lines
Method. Look at the picture.
- Read the picture. Arrows show the direction the light travels in the picture.direction
- Write the answer. arrow
Check. Rays are lines with arrows. ✓
Method. Read the idea.
- Read the idea. Light appears to travel in straight lines.straight lines
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. Light travels in straight lines from a source. ✓
Method. Think about the holes.
- Think about the holes. The holes are in a straight line with the torch and the wall.straight line
- Decide. So the light reaches the wall, and the answer is yes.yes
- Write the answer. yes
Check. The light passes through all three holes. ✓
Method. Think about the holes.
- Think about the holes. The middle hole is not in line, so the card blocks the light.blocked
- Decide. So the light does not reach the wall.no
- Write the answer. no
Check. Light is blocked by the card. ✓
Method. Read the idea.
- Read the idea. An opaque material blocks light.blocks light
- Write the word. So the word is opaque.opaque
- Write the answer. opaque
Check. A card is opaque. ✓
Method. Read the idea.
- Read the idea. A transparent material lets light pass through clearly.through clearly
- Write the word. So the word is transparent.transparent
- Write the answer. transparent
Check. Clear glass is transparent. ✓
Method. Read the definition.
- Read the definition. A straight line of light with an arrow is a ray.ray
- Write the answer. ray
Check. Rays are drawn in diagrams. ✓
Method. Use the straight line idea.
- Use the idea. Light travels in straight lines, so it is blocked by the card.blocked
- Decide. So the answer is no.no
- Write the answer. no
Check. The card casts a shadow. ✓
Method. Check the idea of straight lines.
- Check the idea. Light appears to travel in straight lines, and does not bend round a card.straight lines
- Decide. So Priya is not right.no
- Write the answer. no
Check. Light does not bend round an object in this model. ✓
Method. Count the holes.
- Count. The light passes through each of the three holes.three holes
- Write the number. So the light passes through 3 holes.3
- Write the answer. 3
Check. All three holes are in the straight path. ✓
Method. Think about what makes the test fair.
- Think about the test. The test changes only the position of one hole, and everything else is kept the same.one change
- Write one thing. For example, use the same torch each time.same torch
- Write the answer. Accept any one of: the torch, the position of the cards, the distance between the cards.
Check. Only one hole should be moved. ✓
Method. Think about straight lines.
- Think about the path. Light travels in a straight line from the torch to the wall.straight
- Think about the hole. A hole that is not on that line lets no light through; the card blocks it.blocks
- Write the answer. Accept any sentence that says light travels in straight lines, so the light cannot pass through a hole that is not in line.
Check. This shows the straight-line path clearly. ✓
Method. Think about the test.
- Think about the holes. Light passes through all three holes only when they are in a line.in a line
- Think about the path. So the path is straight, not curved.straight
- Write the answer. Accept any sentence that says the light passes through three holes only when they are in a straight line, so its path is straight.
Check. A curved path would not pass through all three holes. ✓