Light travels in straight lines booklet
Light travels in straight lines booklet
- Unit 1: Living things
- Unit 2: Energy
- Unit 3: Materials
- Unit 4: Earth and its habitats
- Unit 5: Light
- Unit 6: Electricity
🌟 This Topic is About...
- I will investigate how light travels.
- I will make a prediction and test whether the results support it.
- I will draw a conclusion from my results.
- I will learn how to draw a ray diagram to show how light moves.
Let’s discover how light travels and helps us see the world!
🌟 Key Words
- proof
- prove
- ray
- ray diagram
📖 Tap to Learn the Meanings!
- 📜 proof: clear evidence or facts that show something is true.
- 🧠 prove: to show by testing or reasoning that something is true.
- 🌞 ray: a straight line of light traveling from a light source.
- 🔆 ray diagram: a drawing that shows how light rays travel, reflect, or refract.
Great job learning new words! 🎉
You can see in pictures that light travels in straight lines. But as a scientist you need to get evidence to prove (show) that this is true.
The next investigation will give you proof – evidence that shows that something is true.
Quick Fact
In science, we build evidence with observations and experiments. When the evidence strongly supports an idea, we say it’s proven for the tested conditions.
🔬 Think like a Scientist: Prove that Light Travels in Straight Lines
Question: How can we show that light travels in straight lines?
You will need: A flexible plastic tube and a flashlight with batteries 🔦
📝 Method:
- Predict whether your partner will see the light if you shine the flashlight down the tube.
- Shine your flashlight down the plastic tube.
- Can your partner see the light when they look down the other end of the tube?
- Now make a bend in the tube.
- Predict whether your partner will see the light if you shine the flashlight down the bent tube.
- Shine your flashlight down the tube again.
- Can your partner see the light now when they look down the other end?
- What do you conclude about how light travels?
💡 Light travels in straight lines, so when the tube is bent, the light cannot reach the other end.
❓ Questions:
🌟 Tap to See Answers
- 1: Yes, when the tube was straight, light could travel directly through it and be seen at the other end.
- 2: When the tube was bent, your partner could no longer see the light because it couldn’t bend around the corner.
- 3: This shows that light travels in straight lines and cannot curve around obstacles.
Brilliant experiment! You’ve proven one of the key properties of light.
Light rays
Look again at the photographs of light travelling from the Sun and the film projector.
In both photographs you can see the light is travelling in straight lines. Each narrow beam of light is called a ray. Light rays travel from the source of light in all directions until they hit something.
Ray diagrams
We can show how light travels with a ray diagram. On the diagram, we draw straight lines for the rays of light. We draw an arrowhead to show the direction the light ray is moving. Here is an example of a ray diagram with light rays travelling from a lamp.
Imagine a light ray from the lamp hits an object such as a book. This light ray is an arriving ray. The light rays will bounce or reflect off the book. These rays are called reflected rays. The reflected rays are also straight lines but they travel in a different direction to the rays leaving the light source. If the reflected rays enter our eyes we will see the book. Here is a ray diagram to show this.
Let’s revisit the coin in the box. We can show how light travels using a ray diagram.
Quick Fact
When light hits a shiny surface, it reflects at the same angle it arrives. This predictable behavior helps us understand how mirrors and reflections work.