Question

Hypermetropia can be corrected by using :

• A. concave lens
• B. convex lens
• C. combination of both convex and concave lens
• D. none of these

Hint:

Remember the common eye defects and their corrections:
{Myopia (Short-sightedness):} Can see near objects clearly, distant objects are blurry. Light focuses {in front} of the retina. Corrected with a {concave lens} (diverging).
{Hypermetropia (Long-sightedness):} Can see distant objects clearly, near objects are blurry. Light focuses {behind} the retina. Corrected with a {convex lens} (converging). Hypermetropia needs {more} converging power, which a convex lens provides.

Answer 1

The Correct Option is B

Concept: Hypermetropia, also known as long-sightedness or far-sightedness, is a common vision defect where a person can see distant objects clearly but has difficulty seeing nearby objects clearly. Step 1: Understanding Hypermetropia In a hypermetropic eye, the light rays from a nearby object are focused {behind} the retina, instead of directly on it. This can happen for two main reasons: (A) The eyeball is too short (axial hypermetropia). (B) The converging power of the eye lens is too weak (or the focal length of the eye lens is too long) (refractive hypermetropia). As a result, the image of a nearby object formed on the retina is blurred. The near point of a hypermetropic eye is further away than the normal near point (25 cm). Step 2: How to correct Hypermetropia To correct hypermetropia, a lens is needed that can help the eye lens converge the light rays from nearby objects onto the retina. This requires increasing the overall converging power of the eye's optical system. A convex lens (converging lens) is used for this purpose. The convex lens adds converging power, causing the light rays from a nearby object to converge more strongly, so that they focus correctly on the retina. Step 3: Analyzing the options for corrective lenses
(1) Concave lens: A concave lens is a diverging lens. It is used to correct myopia (short-sightedness), where the eye lens converges light too strongly or the eyeball is too long.
(2) Convex lens: A convex lens is a converging lens. It adds converging power and is used to correct hypermetropia.
(3) Combination of both convex and concave lens (Bifocal or Progressive lens): This type of lens (e.g., bifocal) is used to correct presbyopia (age-related difficulty in focusing on near objects, often occurring in individuals who may also have myopia or hypermetropia for distance). It might also be used for complex refractive errors, but for simple hypermetropia, a convex lens is the direct correction.
(4) None of these: Incorrect, as convex lens is the correct solution. Therefore, hypermetropia can be corrected by using a convex lens.