Lakhmir Singh and Manjit Kaur Solutions for Chapter: The Human Eye and The Colourful World, Exercise 7: Short Answer Type Questions

Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.

Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and how it is corrected by a lens.

A person suffering from eye-defect myopia (short-sightedness) can see clearly only up to a distance of $2 \mathrm{m}$. What is the nature and power of the lens required to rectify this defect?

The near point of a person suffering from hypermetropia is at $50 \mathrm{c}\mathrm{m}$ from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near point of the normal eye is $25 \mathrm{c}\mathrm{m}$).

A person needs a lens of power, $-5.5 \mathrm{D}$ for correcting his distant vision. For correcting his near vision, he needs a lens of power, $+1.5 \mathrm{D}$. What is the focal length of the lens required for correcting distant vision.

A person needs a lens of power, $-5.5 \mathrm{D}$ for correcting his distant vision. For correcting his near vision, he needs a lens of power, $+1.5 \mathrm{D}$. What is the focal length of the lens required for correcting near vision.

What is presbyopia? Write two causes of this defect. Name the type of lens which can be used to correct presbyopia.

When is a person said to have developed a cataract in his eye? How is the vision of a person having cataract restored?