An eye lens forms a real, inverted image 2 cm behind the retina for a distant object. What error in the eye's structure could cause this situation?
Eyeball shorter than normal
For clear vision the eye lens must focus the image exactly on the retina. Here the image of a distant object is formed behind the retina, which is the condition of hypermetropia (long-sightedness or far-sightedness), where the rays converge too little before reaching the retina.
One structural cause of this defect is an eyeball that is too short: the retina lies closer to the lens than normal, so the light rays reach it before they meet, and the focused image falls behind it. The other cause is a lens with too long a focal length (too weak).
A lens more curved than normal is too powerful and an eyeball longer than normal places the retina too far away; both make the image form in front of the retina, which is myopia (short-sightedness), not this case.
Thickening of the retina does not shift the focal point of the lens by 2 cm, so it does not explain an image formed behind the retina. Hypermetropia is corrected with a convex (converging) lens.
Hence, Eyeball shorter than normal.
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Important Questions from Optics
Who was the first one to use a glass prism to obtain the spectrum of sunlight?
Twinkling of stars is due to:
In which a convex mirror is used?
A. Rear View mirrors in vehicles
B. Glass windows
C. Makeup Mirror
D. Kaleidoscope
An object is placed 10 cm in front of a lens. The image formed is real, inverted and of same size as the object. What is the focal length and nature of the lens?
The power of a lens is -2.5 D. The type of lens and its focal length are respectively:
