A Myopic person can see things clearly if they lie between 8cm And 100cm from his eye. The lens will enable him to see the moon distinctly if its focal length is ____cm.

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Detailed Solution

Concept: The lens will enable him to see the moon distinctly if its focal length is 100cm.
A slightly enlarged eyeball that reflects light in front of the retina rather than directly on it is the cause of myopia. While myopia can be reduced and improved distance vision made possible through the use of glasses, contact lenses, eye drops, and surgery, these measures merely address the disease's symptoms.
We are aware that the moon is located at an infinite distance. Hence,
u = −∞
We are also aware that if the object is at infinity then the image is formed at focal length. Now,
f = −100cm
Myopic is corrected by concave lenses in eyeglasses. Because of the longer than normal distance between the lens and retina, near-sighted people have trouble seeing distant objects well. A nearsighted eye with concave lenses in front of it allows for the creation of vision on the retina by reducing light refraction and lengthening the focus length.
Therefore, if the concave lens' focal length is 100 cm, he will be able to clearly see the moon.
Hence, the correct answer is -100 cm.

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