Refraction
This Topic is About...
- I will learn how light bends when it moves from one material to another. This is called refraction.
- I will use diagrams to show how refraction happens.
- I will ask scientific questions and choose the best investigations to answer them.
- I will make predictions and check if they were correct.
- I will use books and other information sources to help answer my questions.
- I will make a conclusion using what I learn about refraction.
You’re going to be a science explorer!
Key Words
- converge
- convex lens
- focal point
- lens
- medium
- optical illusion
- prism
- rainbow
- refraction
- refracts
Tap to Learn the Meanings!
- converge: When rays of light come together to meet at a point.
- convex lens: A lens that curves outward and brings light rays together.
- focal point: The point where rays of light meet after passing through a lens.
- lens: A curved piece of transparent material that bends light.
- medium: A material that light travels through, like air, water, or glass.
- optical illusion: Something that tricks the eyes into seeing differently from reality.
- prism: A transparent shape that bends light and can split it into colours.
- rainbow: A band of colours formed when white light splits after refraction.
- refraction: The bending of light when it moves from one medium to another.
- refracts: The action of light bending as it passes through a new medium.
Great job learning new science words!
Light Bending Magic
Refraction is the bending of light. Refraction happens because light travels at different speeds through different materials.
What Is a Medium?
Amedium is a material that light travels through. Examples of mediums include air, water and glass.
Seeing the Fish Trick
Look at the picture of Sofia. She is looking at the fish in the water. She thinks the fish is in a straight line from her eyes, but it is not.
Optical Illusion Surprise
An optical illusion is something our eyes see that looks real but is not. The fish looks higher than it really is because the light bends.
Light Changing Direction
The ray of light from the fish bends, or refracts, as it travels from the water into the air. This bending makes the fish appear in a different place.
Think like a scientist — Demonstrate how light travels when it refracts
You will need: a glass of water and a pencil
Method:
- Predict what you will see when you put the pencil into the water.
- Put the pencil in the glass of water.
- Observe the pencil in the glass from the side.
- Observe the pencil in the glass from the top.
- Take out the pencil. Is it changed in any way?
Questions:
Light from the pencil travels through the ________ in the glass and then ________ when it passes through the glass to the ________.
How are we doing?
How well have you and your group done the demonstrations?
How well can you explain what happened using your scientific knowledge of refraction?
Choose from:
“We can explain refraction well” or “We are learning how to explain refraction” or “We need some help”
What Is a Lens?
Alens is a transparent substance with at least one curved surface. Lenses refract light in useful ways. Our eyes have lenses in them. Other lenses that we use may be made of glass or transparent plastic.
Lenses in Everyday Life
People have used the science of refraction to make many useful things.
How a Lens Changes Light
The lens bends light rays as they pass through it, so the rays change direction. This means the rays seem to come from a point that is closer or further away than they actually do. This is what makes objects seen through a lens appear either bigger or smaller than they really are.
The Convex Lens Effect
Aconvex lens makes things look bigger. Light rays pass through the lens and bend inward and meet or converge at a point just beyond the lens. This point where the rays converge is called the focal point.
Where Convex Lenses Are Used
Convex lenses are used to make eyeglasses, projectors, microscopes, binoculars and telescopes. The lens brings distant light rays to a focus in our eyes. Some telescopes have such strong lenses that we can see distant planets and moons in the solar system.
Think like a scientist — Make and test a convex lens
You will need: a sheet of newspaper or an old magazine, a piece of plastic wrap, an eye dropper or very small spoon, a cup of water
Method:
- Cut a square of plastic wrap about 10 × 10 cm.
- Place the plastic wrap over some printed words on the newspaper.
- Very carefully, use the dropper or spoon to place a drop of water on the plastic.
- Look at the print and you should be able to see that the water drop magnifies the words. You have made a lens!
Questions:
- What happens if you make the water drop bigger or smaller?
- What happens if you lift the plastic away from the paper?
Test your ideas out.
Try to explain what has happened using your science knowledge.
Prisms and Rainbows
Aprism is a triangular block of glass or clear plastic.
White Light and Colours
We usually see light as having no particular colour. We call this ‘white light’. But white light actually consists of different colours. When a narrow ray of white light passes through a prism, the ray refracts and splits into different colours. Each colour refracts at a different angle.
Seeing a Rainbow in the Sky
Look at the photograph at the beginning of this topic. Have you ever seen a coloured arc in the sky like this? It is called a rainbow. If you have seen one, you will know that it has to be sunny and raining at the same time. The Sun has to be shining behind you and the rain has to be falling in front of you.
Rainbows as Optical Illusions
Arainbow is another optical illusion. It happens when sunlight is refracted as it passes from the air to a raindrop. The raindrops act like tiny prisms. When this happens, our eyes see the seven colours which make up white light.