CBSE Class 10 Science 2020 · Paper 31/4/3 · Question 23
Which defect of the eye is known as far-sightedness ? When does this defect arise ? State two reasons. How is this defect corrected ?
Answer
Far-sightedness is hypermetropia, caused by a long eye-lens focal length or a small eyeball; a convex lens corrects it.
Far-sightedness is hypermetropia. The defect arises when a person can see distant objects clearly but cannot see nearby objects distinctly: the near point of the eye moves farther away than the normal 25 cm, because light from a nearby object is focused behind the retina. Two reasons: (i) the focal length of the eye lens is too long (its converging power has decreased); (ii) the eyeball has become too small, so the retina is too close to the eye lens. It is corrected by using spectacles with a convex (converging) lens of appropriate power, which supplies the extra focusing power needed to form the image on the retina.
🔒 Step-by-step solution
Sign up free to see every step of how it is worked out.
From the board paper
More questions from The Human Eye and the Colourful World
Class 10 Science — every question with an expert-verified, step-by-step solution.
- Q1 The human eye can focus on objects at different distances by adjus…
- Q1 What is meant by power of accommodation of the eye?
- Q2 The human eye forms the image of an object at its
- Q2 A person with a myopic eye cannot see objects beyond 1.2 m distinc…
- Q3 The least distance of distinct vision for a young adult with no…
- Q3 What is the far point and near point of the human eye with norm…
- Q4 The change in focal length of an eye lens is caused by the action…
- Q4 A student has difficulty reading the blackboard while sitting in t…
- Q5 A person needs a lens of power -5.5 dioptres for correcting his dista…
- Q6 The far point of a myopic person is 80 cm in front of the eye. W…
- Q7 Make a diagram to show how hypermetropia is corrected. The near po…
- Q8 Why is a normal eye not able to see clearly the objects placed…
All 281 questions on The Human Eye and the Colourful World → Browse all Science chapters →