A man wears convex lens glasses of focal length 40cm in order to correct his eye defect. instead of the optimum 25cm, his least distance of distinct vision ...

A man wears convex lens glasses of focal length 40cm in order to correct his eye defect. instead of the optimum 25cm, his least distance of distinct vision is

Answer Details

A person with an eye defect has difficulty seeing objects clearly, especially those that are close to them. The defect may be due to the shape of the eye, which prevents light from being focused correctly on the retina. A convex lens can be used to correct this defect by converging the light before it enters the eye, thus allowing the eye to focus the image correctly. The focal length of a lens is a measure of its ability to converge light. A lens with a shorter focal length is more powerful and can converge light more strongly than a lens with a longer focal length. For a person with an eye defect, the focal length of the lens must be chosen to compensate for the defect and provide the correct amount of convergence. In this question, the man wears convex lens glasses with a focal length of 40cm to correct his eye defect. However, his least distance of distinct vision is not the optimum distance of 25cm. The least distance of distinct vision is the minimum distance at which an object can be seen clearly. To find the least distance of distinct vision for this man, we can use the lens equation: 1/f = 1/di + 1/do Where f is the focal length of the lens, di is the distance of the image from the lens, and do is the distance of the object from the lens. For the man to see an object at his least distance of distinct vision, the image formed by the lens must be at infinity (di = infinity). Plugging these values into the lens equation and solving for do gives: 1/40 = 1/infinity + 1/do 1/do = 1/40 do = 40cm Therefore, the man's least distance of distinct vision is 40cm. The correct answer to the question is "150cm," which is not among the answer options provided.