IGCSE 0625 / Section 3.2 / Extended
Supplement (Extended) content

Back onto the retina.

A healthy eye lands a sharp image right on the retina. When the focus falls a little in front or a little behind, the world goes blurry, and the fix is a carefully chosen lens that nudges the image back into place.

The key idea

In short sight, distant objects focus in front of the retina and are corrected with a concave (diverging) lens. In long sight, near objects focus behind the retina and are corrected with a convex (converging) lens.

Definition · learn the exact words

Short sight focuses distant objects in front of the retina and is corrected by a concave (diverging) lens; long sight focuses near objects behind the retina and is corrected by a convex (converging) lens.

short sight: diverging lens · long sight: converging lens

The correcting lens shifts the focus point back exactly onto the retina.

Section 01

Move the focus back to the retina.

Switch between a short-sighted and long-sighted eye, then add the correcting lens and watch the image sharpen.

Stage 1 · Learn

Check correcting sight

Four quick checks. Each correct answer earns XP and lights this skill on your star map.

Quick check+10 XP

In short sight (myopia), distant objects are focused...

Quick check+10 XP

Short sight is corrected using a...

Quick check+10 XP

In long sight, near objects are focused...

Quick check+10 XP

Long sight is corrected using a...

Section 02

Two faults, two lenses.

Each defect focuses the image in the wrong place, and each is corrected by the opposite type of lens.

Short sight (myopia)Long sight (hyperopia)
Distant objects focus in front of the retinaNear objects focus behind the retina
Cannot see far objects clearlyCannot see near objects clearly
Corrected with a concave (diverging) lensCorrected with a convex (converging) lens
The diverging lens spreads rays before the eyeThe converging lens brings rays together sooner
Examiner trap

Short sight is corrected with a concave (diverging) lens, not a converging one, and long sight with a convex (converging) lens. Pairing the defect with the wrong lens is the classic mistake here.

Stage 2 · Exam

Exam-style questions

Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.

Finish the four checks above to unlock the exam questions
Exam style+20 XP

A person who cannot focus on distant objects (short sight) needs spectacles with a...

Exam style+20 XP

A person whose eye focuses near objects behind the retina has...

Exam style+20 XP

A converging (convex) lens is used to correct...

Skill unlocked

Correcting sight, mastered.

Sight correction mastered. Dispersion finishes the light strand.

-Rank -Level -Score -Topics
Go deeper · practice
Six original Cambridge-style questions
Short sight and long sight, where each focuses the image, and the correcting lens for each. Attempt each, then reveal the worked solution.
Stage 3 · master the unit
Waves challenge
Mixed questions across the whole unit, each one worth XP. Start this only when you feel confident across every topic in the unit, not just correcting sight.
Start the unit challenge →