Riya cannot clearly see the bird sitting on a tree with naked eyes. However, when she used her spectacles of power –4 dioptre, she was able to see it clearly. Calculate the focal length of her lens.​

Q. Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her as non-uniform and distorted. The doctor diagnosed the problem as:

Q. A person can see clearly up to 3 metres what should be the power of the lens in his spectacles so that he could see clearly up to 12 metres.

Q. A man can not see clearly kept at less than $150cm$. He wants to read notice at distance $25cm$. What should be the nature and focal length of the lens used in spectacles?

Q. A person is not able to see nearby objects clearly. His vision can be corrected with the help of spectacles containing:

Q. A nearsighted person cannot see objects clearly beyond $25.0cm$ (her far point). If she has no astigmatism and contact lenses are prescribed for her, -'what power and type of lens are required to correct her vision ?