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Primary Science · Year 6Chapter 8 · How we see
Year 6 Science · How we see · Lesson 8.4

Year 6 Science: How the eye works

Part of the Year 6 Science how we see chapter. Chapter overview · whole chapter on one page

8.4

How the eye works

Year 6
L3: light travels from light sources to our eyes; the eye receives the light and sends signals to the brain
Story. Sam closes his eyes in a dark room, then opens them under a bright lamp. “The middle of my eye got smaller,” he says. The nurse explains: “The opening that lets in light, called the pupil, gets smaller in bright light and bigger in dim light.”

The eye is an organ that receives light. Light enters the eye through the pupil, which is the opening in the middle. The lens focuses the light onto the retina at the back of the eye. The retina has light-sensitive cells, which send signals along the optic nerve to the brain. The brain then interprets the signals, so we see the object.

brainpupillensretinaoptic nervelight enters at the pupil, the lens focuses it on the retina
A simple diagram of the eye. Light enters at the pupil, the lens focuses it on the retina at the back, and the optic nerve carries signals to the brain.

The table names the main parts of the eye.

Part of the eyeWhat it does
Pupilthe opening that light enters the eye through; it gets smaller in bright light
Lensfocuses the light onto the back of the eye
Retinathe layer at the back of the eye, with light-sensitive cells
Optic nervecarries signals from the retina to the brain

Key ideas

  • Light enters the eye through the pupil.
  • The lens focuses the light onto the retina.
  • The retina sends signals along the optic nerve to the brain.
  • The pupil gets smaller in bright light and bigger in dim light.
Worked example 8.4.1
Which part of the eye focuses the light onto the back of the eye? Write the word.

Method. Read the table.

  1. Read the table. The lens focuses the light onto the retina.
    lens
  2. Write the word. So the part is the lens.
    lens
  3. Write the answer.
    lens

Check. The lens works like the lens in a camera. ✓

Worked example 8.4.2
Which part of the eye carries signals from the retina to the brain? Write the words.

Method. Read the table.

  1. Read the table. The optic nerve carries signals from the retina to the brain.
    optic nerve
  2. Write the words. So the part is the optic nerve.
    optic nerve
  3. Write the answer.
    optic nerve

Check. The brain then tells us what we see. ✓

Worked example 8.4.3
In bright light, does the pupil get bigger or smaller? Write the word.

Method. Read the description.

  1. Read the description. The pupil gets smaller in bright light.
    smaller
  2. Write the word. So the pupil gets smaller.
    smaller
  3. Write the answer.
    smaller

Check. A smaller pupil lets less light in. ✓

Watch out

Watch out: the eye does not send light to the brain. Light enters the eye, and the retina sends signals to the brain.

Exam tip

Exam tip. Name the eye part and say what it does: pupil lets light in, lens focuses it, retina senses it, optic nerve carries signals.

Try it (with your teacher, or a grown-up at home). Look at your eyes in a mirror in a dim room, then in a brighter room, with a grown-up. Notice whether the dark centre gets bigger or smaller. Do not look at a bright light for a long time, and never look at the Sun.

Exercise 8D  How the eye works

1
FWhich part of the eye is the opening that lets light in? Write the word.
2
FWhat is the job of the lens in the eye? Write the words.
3
FWhich part of the eye is the layer at the back that has light-sensitive cells? Write the word.
4
FWhich nerve carries signals from the retina to the brain? Write the words.
5
FWhere does the light go after it passes through the lens? Write the word.
6
FIn dim light, is the pupil bigger or smaller? Write the word.
7
FDoes the eye send light to the brain? Write yes or no.
8
PSAli says the pupil is the part of the eye that focuses light. Is Ali right? Write yes or no.
9
PSSam goes from a dark room into bright light. Does his pupil get smaller or bigger? Write the word.
10
PSName the two parts of the eye that light passes through, in order, from the front. Write the two words.
11
RExplain why the lens is needed to make the image on the retina clear. Write one sentence.
12
RExplain why we can see things in a dim room, but not clearly in the dark. Write one sentence.
13
RChallenge: explain why the pupil getting smaller in bright light protects the retina. Write one sentence.

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