A person with a defective sight is using a lens having a power of +2D. The lens he is using is

Options

A. concave lens with `f=0.5 m`
B. convex lens with `f=2.0 m`
C. concave lens with `f=0.2 m`
D. convex lens with `f=0.5 m`

Explanation

To solve the question regarding the type of lens a person with defective sight is using, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Power of the Lens**:
The power \( P \) of a lens is defined as the reciprocal of its focal length \( f \) in meters. The formula is given by:
\[ P = \frac{1}{f} \]

2. **Given Power**:
The problem states that the power of the lens is \( +2D \) (diopters). This indicates that the lens has a positive power.

3. **Calculate the Focal Length**:
Using the formula for power, we can rearrange it to find the focal length:
\[ f = \frac{1}{P} \]
Substituting the given power:
\[ f = \frac{1}{2} = 0.5 \text{ meters} \]

4. **Determine the Type of Lens**:
- A positive focal length indicates that the lens is a **convex lens**.
- A convex lens converges light rays and is used for correcting hyperopia (farsightedness).

5. **Conclusion**:
Since the power is positive and the focal length is \( 0.5 \) meters, the lens used by the person is a **convex lens**.

### Final Answer:
The lens the person is using is a **convex lens**.