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The Eye and Defects
Eye focuses on retina; myopia uses concave correction, hypermetropia uses convex correction.
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The Eye and Defects
Your eye focuses light onto the retina.
If the eye focuses light at the wrong position, corrective lenses can help move the focus back onto the retina.
Recommended for Class 10
The Eye and Defects
The human eye is an optical system that focuses light onto the retina.
Cornea
The cornea provides a large part of the eye's refraction.
Lens
The eye lens fine-tunes the focus of incoming light.
Iris and Pupil
The iris controls the size of the pupil and therefore regulates how much light enters the eye.
Retina
The retina contains light-sensitive receptor cells.
A focused image forms on the retina and is converted into nerve signals.
Accommodation
Accommodation is the process by which the eye changes the shape of its lens to focus on objects at different distances.
Myopia — Short-sightedness
A myopic eye focuses distant objects in front of the retina.
It can be corrected using a concave/diverging lens.
Hypermetropia — Long-sightedness
A hypermetropic eye has difficulty focusing nearby objects, with the uncorrected focus tending to fall behind the retina.
It can be corrected using a convex/converging lens.
Presbyopia
With age, the eye lens becomes less flexible and accommodation becomes weaker.
This can make near focusing difficult.
The Eye and Defects — Advanced
The optical power of the eye comes mainly from the cornea and crystalline lens. Accommodation changes the lens curvature and therefore its optical power.
Refractive defects occur when the eye's optical power and axial length do not match correctly.
Common Mistakes
Common Mistakes
- Mistake
Myopia → concave correction.
- Mistake
Hypermetropia → convex correction.
- Mistake
The pupil is an opening, not a lens.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Image on retina.
Myopia → concave.
Hypermetropia → convex.
Accommodation → lens adjustment.
- Definition
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Practice
PQ
Q1. What is the function of the retina?
PQ
Q2. What does the iris control?
PQ
Q3. Define accommodation.
PQ
Q4. How is myopia corrected?
PQ
Q5. How is hypermetropia corrected?
Exam Practice
EQ
Q1. Explain how the eye focuses light.
EQ
Q2. Define accommodation.
EQ
Q3. Explain myopia and its correction.
EQ
Q4. Explain hypermetropia and its correction.
EQ
Q5. What is presbyopia?
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.