Question

When do we say that a particular person is suffering from hypermetropia? List two causes of this defect. Name the type of lens used to correct this defect.

Answer 1

Step 1: Understanding Hypermetropia:
A person is said to be suffering from hypermetropia (also known as farsightedness) when they can see distant objects clearly, but have difficulty focusing on nearby objects. This occurs when the image of a near object is formed behind the retina, rather than on it.

Step 2: Causes of Hypermetropia:
1. Shortened Eyeball:
In hypermetropia, the eyeball is too short from front to back, causing the light entering the eye to focus behind the retina.

2. Weak Lens or Cornea:
In some cases, the lens or cornea of the eye may be too weak or have too little curvature, preventing the light from being focused properly on the retina.

Step 3: Correcting Hypermetropia:
To correct hypermetropia, convex lenses (also known as converging lenses) are used. These lenses help focus the light rays correctly on the retina by converging them before they enter the eye.

Step 4: Conclusion:
- Hypermetropia is a condition where distant objects are seen clearly, but near objects are blurry, due to the image being focused behind the retina.
- Causes include a shortened eyeball or a weak lens/cornea.
- Convex lenses are used to correct this defect by converging the light rays to focus on the retina.