Q.Convex lens is used in (A) short-sightedness
(B) long-sightedness
(C) presbyopia
(D) astigmatism

A positive-power (convex) lens converges light and corrects hypermetropia, in which near objects focus behind the retina.

A power of +2D means a convex (converging) lens. Such a lens is prescribed for hypermetropia (far-sightedness), where the eye's converging power is too weak and the image of a near object would form behind the retina; the added convex lens brings it onto the retina.

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The human eye lens forms a real, inverted image on the retina → option (A).

The eye lens is a converging (convex) lens and the object is well beyond its focal length, so it forms a real, inverted and diminished image on the retina — just as any convex lens does for …

A convex lens corrects long-sightedness (hypermetropia) → option (B).

In long-sightedness (hypermetropia) the eye cannot focus on nearby objects because the image of a near object forms behind the retina (the eye's converging power is too weak). A convex (converging) lens adds the extra converging power needed to bring the image forward …

The eye's retinal image is real and inverted.

The eye lens is a converging (convex) lens. For real objects placed beyond its focal length, a convex lens forms a real, inverted, diminished image. This image falls on the retina, so i …

A convex (converging) lens corrects farsightedness (hypermetropia).

In farsightedness (hypermetropia) the eye's near point recedes beyond 25 cm — nearby objects focus behind the retina because the eye's converging power is too weak. A convex lens adds the missing converging power, bringing the …

The eye-lens focal length is about 2 cm.

The human eye focuses the image of an object on the retina, which lies roughly 2.5 cm behind the eye-lens. To image a distant object on the retina, the effective focal length of the relaxed eye-lens must be of the same order — about 2 cm. Optio …

The near point (least distance of distinct vision) of a normal eye is conventionally taken as $D = 25$ cm.

The least distance of distinct vision ($D$) is the closest distance at which the eye can focus on an object clearly without strain, using its full accommodation. For a normal (young, healthy) human eye, this is standardised at …