A person wears glasses with power -2.5 D. Without glasses the person

Options

A. cannot see near objects clearly
B. cannot see objects clearly beyond 25 cm
C. cannot see objects clearly beyond 30 cm
D. cannot see objects clearly beyond 40 cm

Explanation

To solve the problem, we need to analyze the information given about the person's glasses and their vision condition. The person wears glasses with a power of -2.5 D, which indicates that they have myopia (nearsightedness).

### Step-by-Step Solution:

1. **Understanding Lens Power**:
- The power (P) of a lens is given by the formula:
\[ P = \frac{1}{f} \]
where \( f \) is the focal length of the lens in meters. The unit of power is diopters (D).

2. **Calculating Focal Length**:
- Given the power of the lens is -2.5 D, we can find the focal length:
\[ f = \frac{1}{P} = \frac{1}{-2.5} = -0.4 \text{ meters} \]
- Converting this to centimeters (1 meter = 100 centimeters):
\[ f = -0.4 \times 100 = -40 \text{ cm} \]
- The negative sign indicates that it is a concave lens.

3. **Interpreting Focal Length**:
- The focal length of -40 cm means that the lens can focus light coming from objects that are closer than 40 cm.
- For a person with myopia, this means they can see clearly up to 40 cm but cannot see objects clearly beyond this distance.

4. **Conclusion**:
- Therefore, without glasses, the person cannot see objects clearly that are farther away than 40 cm.

### Final Answer:
The person cannot see objects clearly beyond 40 centimeters.

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