Describe what happens to the ciliary muscle, suspensory ligaments and the shape of the lens when the eye focuses on a near object.
Answer
Ciliary muscle contracts, suspensory ligaments slacken, and the lens becomes more convex.
The correct answer is Ciliary muscle contracts, suspensory ligaments slacken, and the lens becomes more convex. — The increased power brings the image of the near object onto the retina.
Step-by-step solution
- When a near object is to be seen, the brain signals the ciliary muscle to contract.
- Contraction of the ciliary muscle reduces tension on the suspensory ligaments, causing them to slacken.
- With reduced tension, the elastic lens becomes more curved (more convex), increasing its refractive power.
- The increased power brings the image of the near object onto the retina.
Common mistake: Confusing contraction of the ciliary muscle with relaxation of the ligaments.
Concept tested: Accommodation for near vision
Published · How this solution was prepared and checked
Related questions
- 1 Which of the following statements correctly describes the changes that occur in the eye during accommodation for a near object?
- 2 A person with a myopic eye can see clearly up to a distance of 1.2 m. What is the nature and power of the lens required to correct this defect of vision?
- 3 A myopic person sees distant objects clearly only up to a far point of 50 cm. What is the minimum power of a lens (in dioptres) required to correct his vision so that he can see objects at infinity clearly? Assume a thin lens placed close to the eye.
- 4 Which part of the eye contributes the greatest refractive power?
- 5 List three common causes of eye injuries in daily life and suggest one preventive measure for each cause.
- 6 A hyperopic person can see distant objects clearly but cannot read a newspaper held at 25 cm without glasses. The far point of his eye is at infinity. Calculate the minimum power (in dioptres) of a thin converging lens that should be placed close to the eye to enable him to read at 25 cm.