Lakhmir Singh and Manjit Kaur Solutions for Chapter: The Human Eye and The Colourful World, Exercise 8: Long Answer Type Questions

What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show the eye-defect short-sightedness. Also, show the correction of short-sightedness by using a lens.

A person having short-sight cannot see objects clearly beyond a distance of $1.5 \mathrm{m}$. What would be the nature and power of the corrective lens to restore proper vision?

What is long-sightedness? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show the eye-defect long-sightedness and correction of long-sightedness by using a lens.

An eye has a near point distance of $0.75 \mathrm{m}$. What sort of lens in spectacles would be needed to reduce the near point distance to $0.25 \mathrm{m}$? Also, calculate the power of the lens required. Is this eye long-sighted or short-sighted?

An eye has a far point of $2 \mathrm{m}$. What type of lens in spectacles would be needed to increase the far point to infinity? Also, calculate the power of the lens required. Is this eye long-sighted or short-sighted?