Chapter 1 of 7

All 7 chapters
  1. 1Where light comes from, readunderstood
  2. 2Light goes in straight lines, readunderstood
  3. 3How we see, readunderstood
  4. 4Opaque, translucent, transparent, readunderstood
  5. 5Big and small shadows, readunderstood
  6. 6A shadow stick through the day, readunderstood
  7. 7Mirrors and shiny things, readunderstood

S2.6.1 Chapter 1

Where light comes from

The Moon shines at night. Does the Moon make its own light?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Name things that make their own light
  • Tell a light source from a thing that only sends light back
  • Explain why you see nothing in total darkness

Look around the room. Some things seem to shine. Do they all make their own light?

A light source is a thing that makes its own light. The Sun is a light source. So is a fire. Lit candles, lamps and torches are sources too. Some animals, such as fireflies, make light in their bodies.

A lamp with seven arrows going out from it in every direction. Labels: Lamp, light goes out.Lamplight goes out
A lamp is a light source. Its light goes out in every direction.

The Moon looks bright at night. But the Moon makes no light of its own. Light from the Sun falls on it. The Moon sends some of it back. We say the Moon reflects light. To reflect is to send light back.

A mirror and white paper do the same. They make no light. They only reflect the light that falls on them.

Shine a torch on a mirror. The mirror sends the torch light on. All the light came from the torch.

A flat mirror lies along the bottom, labelled Mirror. A ray of light, labelled torch light, comes down to it from the upper left. A second ray, labelled sent back, leaves it to the upper right. A dashed line stands straight up from the mirror.Mirrortorch lightsent back
The mirror makes no light. It sends the torch light back.

Draw it first

Draw how moonlight reaches you

  1. The Sun on the left and the Moon on the right. An arrow labelled sunlight goes from the Sun to the Moon. A second arrow goes from the Moon into an eye. Labels: Sun, Moon, sunlight, Eye.Sun

    1 Draw the Sun on the left. Write "Sun" under it.

  2. The Sun on the left and the Moon on the right. An arrow labelled sunlight goes from the Sun to the Moon. A second arrow goes from the Moon into an eye. Labels: Sun, Moon, sunlight, Eye.SunMoon

    2 Draw the Moon on the right. Write "Moon" under it.

  3. The Sun on the left and the Moon on the right. An arrow labelled sunlight goes from the Sun to the Moon. A second arrow goes from the Moon into an eye. Labels: Sun, Moon, sunlight, Eye.SunMoonsunlight

    3 Draw an arrow from the Sun to the Moon. This is sunlight.

  4. The Sun on the left and the Moon on the right. An arrow labelled sunlight goes from the Sun to the Moon. A second arrow goes from the Moon into an eye. Labels: Sun, Moon, sunlight, Eye.SunMoonsunlightEye

    4 Draw an eye below. Draw an arrow from the Moon into the eye.

Darkness is no light at all. In total darkness you can see nothing. A white paper, a mirror and the Moon all vanish from sight.

An eye on the left and a paper on the right. The paper is dotted to show that it is dark. There are no arrows, because there is no light at all. Labels: no light at all, Eye, Paper.no light at allEyePaper
With no light at all, the eye sees nothing. Not even white paper.

See it three ways

As a picture

Two rows. The top row, makes its own light, shows the Sun, a candle, a lamp and a torch. The bottom row, only sends light back, shows the Moon and a mirror. Labels: makes its own light, only sends light back, Sun, Candle, Lamp, Torch, Moon, Mirror.makes its own lightSunCandleLampTorchonly sends light backMoonMirror

In words

A source makes light. The Moon and a mirror only send light back. With no source, there is no light at all.

Try it

Does paper make light?

You need: a torch, a sheet of white paper, a room that you can make dim.

Be safe: Never shine a torch into anyone's eyes. Do not look into the torch.

  1. Make the room as dim as you can. Close the curtains. If it stays bright, wait for evening.
  2. Hold up the paper. Look at it. It looks dark.
  3. Turn on the torch. Shine it on the paper.
  4. Turn the torch off. Look at the paper again.

What you will see: The paper is bright only while the torch shines on it. The paper makes no light. It reflects the light of the torch.

If you cannot try it, this is what happens.
Two pictures. In the top one, a torch is on and three arrows of light go to a white paper. In the bottom one, the torch is off and the paper is dotted to show it is dark. Labels: Torch on, Torch off, Paper.Torch onPaperTorch offPaper

A wrong idea many people have

The Moon makes its own light.

Why it feels right: The Moon is the brightest thing in the night sky.

The test that breaks it: Look at a thin Moon just after sunset. Its bright side faces where the Sun went down. Only the side that faces the Sun is lit. The Moon is like the paper. The Sun is like the torch.

What is true: The Moon only reflects sunlight. The Sun makes the light.

Key words

light source
a thing that makes its own light.
reflect
to send light back.
darkness
no light at all.

Back to your guess

The answer is B: No. The Moon sends back light from the Sun.

The Moon makes no light of its own. Sunlight falls on it. The Moon sends some of it back to us.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. Which of these is a light source?

    Tap your answer.

    1. Not this one. The Moon looks bright. It only sends back light from the Sun. Try another.

    2. Not this one. A mirror makes no light. It only sends back the light that falls on it. Try another.

    3. Not this one. Paper makes no light. It looks bright only when light falls on it. Try another.

    4. Yes, that is right. A flame makes its own light. The Moon, a mirror and paper only send light back.

    See the answer

    A lit candle

    A flame makes its own light. The Moon, a mirror and paper only send light back.

    • If you chose A: The Moon looks bright. It only sends back light from the Sun.
    • If you chose B: A mirror makes no light. It only sends back the light that falls on it.
    • If you chose C: Paper makes no light. It looks bright only when light falls on it.

  2. Why does the Moon look bright at night?

    Tap your answer.

    1. Yes, that is right. The Sun is the light source. The Moon reflects some of its light to us.

    2. Not this one. It looks that way, but the Moon makes no light. Think of the paper and the torch. Try another.

    3. Not this one. The Moon does not burn. It shines because sunlight falls on it. Try another.

    See the answer

    It sends back light from the Sun.

    The Sun is the light source. The Moon reflects some of its light to us.

    • If you chose B: It looks that way, but the Moon makes no light. Think of the paper and the torch.
    • If you chose C: The Moon does not burn. It shines because sunlight falls on it.

  3. You are in a room with no light at all. You hold up a white paper. What do you see?

    Tap your answer.

    1. Not this one. Paper makes no light. With no light to send back, it cannot be seen. Try another.

    2. Not this one. Eyes cannot make light. With no light at all, there is nothing to see. Try another.

    3. Yes, that is right. With no light, nothing can be seen. Paper only reflects light, and here there is none to reflect.

    See the answer

    Nothing

    With no light, nothing can be seen. Paper only reflects light, and here there is none to reflect.

    • If you chose A: Paper makes no light. With no light to send back, it cannot be seen.
    • If you chose B: Eyes cannot make light. With no light at all, there is nothing to see.

  4. A firefly glows in the dark. Is a firefly a light source?

    Tap your answer.

    1. Yes, that is right. A firefly glows with no other light near it. It makes its own light.

    2. Not this one. A firefly still glows in the dark. A thing that only reflects light would vanish. Try another.

    3. Not this one. A flame, a lamp and a firefly make light too. The Sun is only one source. Try another.

    See the answer

    Yes. It makes its own light.

    A firefly glows with no other light near it. It makes its own light.

    • If you chose B: A firefly still glows in the dark. A thing that only reflects light would vanish.
    • If you chose C: A flame, a lamp and a firefly make light too. The Sun is only one source.

  5. Write three things that make light. Write three that only send it back.

    See the answer

    Make light: the Sun, a candle, a torch. Only send light back: the Moon, a mirror, white paper.

    A thing that makes light is a source. A thing that only reflects light is not a source.

  6. A torch shines on a mirror. A bright spot appears on the wall. Where does that light come from?

    Tap your answer.

    1. Not this one. A mirror makes no light. It only sends back the torch light. Try another.

    2. Not this one. A wall makes no light either. The spot is bright only because light reaches it. Try another.

    3. Yes, that is right. The torch is the source. The mirror reflects its light to the wall. Switch the torch off and the spot is gone.

    See the answer

    The torch. The mirror sends it on.

    The torch is the source. The mirror reflects its light to the wall. Switch the torch off and the spot is gone.

    • If you chose A: A mirror makes no light. It only sends back the torch light.
    • If you chose B: A wall makes no light either. The spot is bright only because light reaches it.

Keep it

Copy this into your exercise book.

A light source makes its own light. The Sun, a fire and a lamp are sources. The Moon, a mirror and paper only send light back. With no light, we see nothing.

Draw: Draw the Sun and the Moon. Draw an arrow between them. Add an eye and an arrow into it.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

No internet tomorrow? Save the whole book as one file (644 KB). It opens on any phone.