$A$ person suffering from an eye defect uses lenses of power $-1\, D$. Name the defect he is suffering from and the nature of lens used.

What is meant by the least distance of distinct vision?

List two causes leading to myopia of the eye. Draw ray diagrams to show the image formation in case of a defective eye and a corrected eye.

How can you identify the type of vision defect a person is suffering from by physically touching their spectacles?

Describe an experiment to discuss the recombination of dispersed light.

$A$ person suffering from an eye defect uses lenses of power $-1 \,D$. Identify the eye defect. Draw a suitable diagram to illustrate how this type of lens corrects the defect. Give the nature of the corrective lens to be used. Also,calculate the focal length of the corrective lens.