The power of a lens of focal length 0.5 m is :

Options

A. `+5 D`
B. 2 D
C. `-5 D`
D. `+1 D`

Answer

To find the power of a lens given its focal length, we can use the formula:

\[ P = \frac{1}{f} \]

where:
- \( P \) is the power of the lens in diopters (D),
- \( f \) is the focal length of the lens in meters (m).

### Step-by-Step Solution:

1. **Identify the Focal Length**:
The focal length \( f \) is given as 0.5 m.

2. **Use the Power Formula**:
Substitute the focal length into the power formula:
\[ P = \frac{1}{f} = \frac{1}{0.5} \]

3. **Calculate the Power**:
\[ P = \frac{1}{0.5} = 2 \text{ D} \]

4. **State the Unit**:
The unit of power is diopters (D).

5. **Conclusion**:
The power of the lens is 2 diopters.

### Final Answer:
The power of the lens of focal length 0.5 m is **2 diopters**.

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