Teacher sheet · Ages 10–11 · about 45–50 minutes
Inside the eye: from light to a picture
Lesson page: echoesof.science/school/eyes/ages-10-11/ · Pupil worksheet: echoesof.science/school/eyes/ages-10-11/print/
Learning aims
- Describe the path of light through the eye and the job of each part.
- Compare rods and cones and explain the fovea and the blind spot.
- Describe nearsightedness, farsightedness and red-green colour blindness simply.
- Carry out a fair test with repeats and means.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: close one eye and try to touch two pencil tips together. Why is it harder? |
| 10 min | Read the text; label an eye diagram. |
| 20 min | Blind-spot fair test in pairs. |
| 5 min | Game: Which part of the eye? |
| 5 min | Quiz. |
Materials for the experiment
- A white card with a black X on the left and a black O on the right, about 7 cm apart
- A ruler or tape measure
- A partner
- Results table
Safety: Measure to the cheekbone, never point a ruler or pencil at an eye. Keep the card a comfortable distance away and stop if your eyes feel tired.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| We see with our eyes alone. | The eye makes signals; the brain builds the picture and even fills in the blind spot. |
| The lens does all the focusing. | The cornea does about two-thirds of it. |
| Colour-blind people see only black and white. | The most common kind mainly makes some reds and greens hard to tell apart. |
Worksheet answers
- Cornea, pupil, lens, retina.
- For example: rods work in dim light but see only grey; cones need more light and see colour.
- Answers vary; the two means are usually similar.
- The brain fills in the gap where there are no light-sensitive cells.
Quiz answers
- Which part controls how much light enters the eye? The iris. The iris controls the size of the pupil.[1]
- Which cells let you see in dim light, but only in grey? Rods. Rods are very sensitive but do not see colour.[2]
- What is special about the fovea? It is packed with cones and gives the sharpest vision. The fovea has many cones.[2]
- Why can't you see anything at the blind spot? There are no light-sensitive cells where the optic nerve leaves. No photoreceptors means no signal from that spot.[3][8]
- In nearsightedness, what looks blurry? Far-away things. The eyeball is a bit too long, so distant things blur.[6]
- Why is red-green colour blindness more common in men? The gene is on the X chromosome, and men have only one X. Women would need the gene on both X chromosomes.[7]
Going further
Draw a large X and O on the board with a coloured background. Does the vanishing O turn white or the background colour? What does that tell you about the brain?
Sources used in this lesson
- [1] How the Eyes Work (National Eye Institute (NIH, USA)): reliability High
- [2] Biology 2e, 36.5 Vision (OpenStax, Rice University): reliability High
- [3] Anatomy and Physiology, 14.1 Sensory Perception (OpenStax, Rice University): reliability High
- [4] College Physics 2e, 26.1 Physics of the Eye (OpenStax, Rice University): reliability High
- [6] Types of Refractive Errors (National Eye Institute (NIH, USA)): reliability High
- [7] Causes of Color Vision Deficiency (National Eye Institute (NIH, USA)): reliability High
- [8] Blind Spot (lecture demonstration) (Physics Lecture Demonstrations, University of Colorado Boulder): reliability Medium-high
Full list with links and a note on each source's reliability: echoesof.science/school/eyes/sources/
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