Y05W08RC The Rainbow Code

This week, you will explore the science behind a rainbow. You will practise following the stages in a process and understanding key light words as you read. Keep an eye on how one step leads to the next. A rainbow may look simple, but a lot is happening inside it.

Informative — Explanation text

An explanation text is a piece of writing that shows how or why something happens. Writers use it to inform you clearly by breaking an idea into connected stages. It usually includes facts, definitions, cause-and-effect links and a clear sequence, often organised with headings and sections that guide you through each part. As a reader, you need to follow the steps carefully and notice how each new part builds on the one before it. You are working out a process, not just collecting separate facts.

Before You Read

  • Look at the title and notice that it points to a natural event that can be explained step by step.
  • Think about how some things in nature seem sudden, but actually happen through a chain of small stages.
  • Get ready to notice headings and any diagram details that help show the order of events.

While You Read

  • Pause after each section and check what new stage has been added to the process.
  • Use the headings as signposts so you can track where the explanation begins, changes and ends.
  • Pay close attention to science words and match them to the definitions around them.
  • Notice cause-and-effect words that show why one step leads to another.
  • If the diagram description appears, use it to picture the path of light through each stage.

Read With Purpose

  • Notice how light changes as it moves through each stage.
  • Pay attention to the science words that explain why colours appear.
  • Watch how the full process builds from one clear step to the next.

Now read

The explanation text

~4 min read · ~605 words

How Rainbows Appear

Intro

A rainbow can seem magical, but it is a weather event that can be explained with science. You do not need paint in the sky to make one. A rainbow appears when sunlight meets tiny water droplets in the air and the light changes direction in a special way. To understand this, it helps to know what light does when it moves from air into water.

Light and refraction

Sunlight may look white or colourless, but it is actually made of many colours mixed together. When light travels through air, it moves in a straight line. However, when it enters a droplet of water, it slows down a little and bends. This bending is called refraction. Refraction happens because light moves at different speeds in different materials.

You can see a similar effect if you place a straw in a clear glass of water. The straw seems bent where the air and water meet. It has not really changed shape. Instead, the light from the straw has bent before reaching your eyes. In a rainbow, sunlight bends as it enters each droplet.

Droplets act like prisms

A raindrop may look simple, but it can act like a tiny prism. A prism is a clear object, often made of glass, that bends light and can split it into colours. Each droplet in the air can do something similar.

First, sunlight enters the droplet and bends. Next, the light bounces off the inside surface of the droplet. Then it leaves the droplet and bends again as it moves back into the air. These steps happen very quickly, but they are important. They help change the path of the light so some of it reaches your eyes.

Optional labelled diagram description

  • Sunlight enters the droplet
  • Light bends as it enters
  • Light reflects inside the droplet
  • Light bends again as it leaves
  • Separated colours travel to the viewer

Why colours separate

The colours in sunlight do not all bend by the same amount. Red light bends a little less, while violet light bends more. Because of this, the colours spread out instead of staying mixed together. This spread of colours is called a spectrum.

That is why a rainbow shows bands of colour rather than one white arc. The colours appear in a regular order because each colour leaves the droplet at a slightly different angle. When millions of droplets are in the air, many of them send the same colour towards your eyes from the same part of the sky. Together, those droplets create the rainbow shape you see.

When you can see a rainbow

You can usually see a rainbow when the Sun is behind you and rain is in front of you. The sky in front needs droplets, but the Sun also needs to be shining. If the light angle is right, the separated colours reach your eyes and form an arc across the sky.

Rainbows are often easier to spot when the Sun is fairly low, such as in the morning or late afternoon. If the Sun is too high, the angle may not work well for you to see the arc. You also need to be in the right place. If another person stands somewhere else, they are seeing light from different droplets, even though both of you may say you are looking at the same rainbow.

A rainbow is not a solid object hanging in one fixed spot. It is the result of sunlight, water droplets and viewing position working together. Once you know the stages, the ‘rainbow code’ becomes much clearer: light enters, bends, reflects, bends again and separates into colour.

Check your vocabulary knowledge

refraction n.
the bending of light when it moves into a new material
prism n.
a clear object that bends and splits light
droplet n.
a very small drop of water
spectrum n.
the full range of colours in light
angle n.
the direction or slant at which something meets or moves