Eye Spy

Eye Spy 👁️

Your eye is a living camera — it bends light, adjusts to focus, and turns the world into signals your brain can read. Learn its parts, how it focuses on near and far, and the simple lenses that fix blurry vision.

The parts of the eye 🔦

The eye is a sense organ full of light receptors. Light travels through it like this: • **Cornea** — the transparent front; it refracts (bends) light, doing most of the focusing. • **Iris** — the coloured ring; it controls how much light enters by changing the **pupil** size. • **Lens** — focuses the light onto the back of the eye, and can change shape. • **Retina** — the light-sensitive layer at the back, full of receptor cells. • **Optic nerve** — carries the impulses from the retina to the brain.

Label the eye

An interactive activity.

Match the job

Focusing: accommodation 🌈

To focus on objects at different distances, the eye changes the **shape of the lens** — this is **accommodation**, controlled by the **ciliary muscles** and **suspensory ligaments**: • **Near** object: ciliary muscles **contract**, ligaments **slacken**, the lens becomes **thicker** (more curved) to refract light strongly. • **Distant** object: ciliary muscles **relax**, ligaments pull **tight**, the lens is pulled **thin** to refract light less.

Focusing up close

To focus on a **nearby** object, what happens to the lens?

• It becomes thicker and more curved
• It becomes thin and flat
• The whole eye gets bigger
• It moves closer to the retina

When focus goes wrong 🔎

If light doesn't focus exactly on the retina, vision is blurred. Two common defects: • **Myopia** (short-sightedness) — distant objects look blurred. The image is focused **in front of** the retina. Corrected with a **concave** (diverging) lens. • **Hyperopia** (long-sightedness) — near objects look blurred. The image would focus **behind** the retina. Corrected with a **convex** (converging) lens.

The right lens

Myopia focuses the image in front of the retina. Which lens corrects it?

• A concave (diverging) lens
• A convex (converging) lens
• No lens can correct it
• A thicker version of the eye's own lens

The optician

An interactive activity.

Fixing sight

Pick the TWO ways (besides glasses) that eyesight defects can be corrected.

• Contact lenses
• Laser surgery to reshape the cornea
• Daily eye drops that regrow the lens
• Squinting harder

In the exam 🎓

Eyes tested. Grade-9 habits for the eye: • Know the parts: **cornea** (refracts), **iris** (controls light), **lens** (focuses/changes shape), **retina** (receptors), **optic nerve** (to brain). • **Accommodation**: lens **thicker** for near, **thinner** for far. • Always say **where** the image forms wrong **and** the correcting lens: **myopia** = in front → **concave**; **hyperopia** = behind → **convex**.