Unit 11 – Sound and Light

11 Sound and Light

How do people use light? Where does the light come from?

In this chapter you will ...

• describe how sound is made.

• describe how sounds can be different.

• list sources of light we use during the day and at night. • list some ways we use sound and light.

Go Online!

Access interactive content relating to this topic on the NGScience website.

ngscience.com

What things around us make sound?

How do people use sound?

Go Online!

Try and guess the secret sounds on the NGScience website. QuickCode: G4S2

What Is Sound?

Close your eyes and listen to the things around you. What can you hear? The things you can hear are sounds. Sound is a form of energy.

What sounds can you hear around you? What is making the sounds?

What Makes Sounds?

Stretch an elastic band over a cup. Pluck the elastic band. What do you see? What do you hear? When you pluck the elastic band, it moves back and forth very quickly – it vibrates. When something vibrates, it makes sound.

How does a guitar make sound?

AB Activities 11.1 – 11.3

Describing Sounds

Engineer It!

Use materials to design a device that makes different sounds. Sounds can be loud or soft.

A jackhammer makes a loud sound.

When you whisper, you make a soft or quiet sound. List some sounds you hear from day to day. Group them as loud or soft sounds.

Sounds can be high or low. The chirp of a baby chick is a high sound. A moo of a cow is a low sound.

AB Activity 11.4

Try This!

With your friends, talk about the different sounds animals make. Which animals make high sounds? Which animals make low sounds?

Using Sound

We use sound in many different ways. We make and use sound when we talk, laugh, cry and sing.

Things we use, like televisions, radios and computers, make sounds.

Sounds made by alarms and sirens are used to alert people.

What are some other ways we use sound?

What Is Light?

Look out of a window during the day. What do you see? You can see the things outside because of light. Light is a form of energy that helps us to see. During the day, the light from the Sun helps us to see.

What are some things that help you to see at night?

At night there is no Sun to light up the things around us. People use light bulbs, flashlights and candles to help see at night.

Amazing Fact!

Sometimes the moon lights up the sky at night. The light from the moon comes from the Sun!

Go Online!

Watch a video about sources of light on the NGScience website. QuickCode: S7Z9

Sources of Light

Something that gives out light of its own is called a source of light. Some sources of light are found in nature. The Sun is a source of light. Fire and lightning are sources of light too.

Flashlights, light bulbs and televisions are sources of light made by people.

AB Activities 11.5 – 11.7

Try This!

Use a flashlight and your hand to make shadows of different shapes. See if your friends can make the same shaped shadows.

Light and Shadows

Sometimes an object can block light and make a shadow. A shadow is a dark area.

Look at the shape of the hand and the shape of the shadow. What do you notice?

AB Activity 11.8

The shape of a shadow is similar to the shape of the object making the shadow.

What things are causing the shadows in the photographs?

Using Light

During the day, we use the light from the Sun to help us see the things around us.

At night, we use lights to light up our cities, streets and homes.

Go Online!

Watch a video on the ways we use light on the NGScience website. QuickCode: M2U9

Cars have headlights that help drivers see at night. Lights also help us to see underwater and underground. You use light when you watch television, play video games, use a computer or use a mobile phone.

What are some other ways we use light?

A Closer Look

Fireflies

Some animals can make light of their own.

Fireflies are beetles that produce light in their abdomens. They use light to signal other fireflies. Their light also tells other animals ‘Don’t eat me. I taste bad!’.

Because fireflies produce light of their own – they are a source of light.

See if you can find other animals that produce light of their own.

Science Words

sound vibrate loud soft high low light source of light shadow

Review

1. True or false. (a) We can hear sounds. (b) Sound is made when something vibrates. 2. Write ‘loud’ or ‘soft’ to describe the sounds. (a) (c) (b) (d)

3. Write ‘high’ or ‘low’ to describe the sounds. (a) (b)

4. True or false. (a) Light is not a form of energy. (b) Light helps us to see the things around us. 5. List two sources of light. 6. What forms when light is blocked by an object? 7. What is causing the shadows? (a) (b)

8. List three ways you use light.

In the Field

An orchestra is a group of people that play musical instruments together to make music. It is important that they play at the right time and they don’t play too loud or too soft. A conductor is a person who stands at the front of an orchestra and lets the musicians know when to play their instrument. They wave their hands to tell the musicians how fast, loud and soft they should play.