Question

What is the focal length of a lens if its power is +2 D?

• A. 0.5 m
• B. 1.0 m
• C. 2.0 m
• D. 0.2 m

Hint:

Remember: The focal length of a lens is the reciprocal of its power: \( f = \frac{1}{P} \).

Answer 1

The Correct Option is A

Given: The power of the lens is \( P = +2 \, \text{D} \). Step 1: Use the formula for power The formula for the power of a lens is: \[ P = \frac{1}{f} \] where \( P \) is the power in diopters, and \( f \) is the focal length in meters. Step 2: Rearrange the formula and solve for \( f \) Rearranging the formula to find the focal length: \[ f = \frac{1}{P} \] Step 3: Substitute the value of \( P \) Substitute \( P = +2 \, \text{D} \) into the formula: \[ f = \frac{1}{2} = 0.5 \, \text{m} \] Answer: The correct answer is option (1): 0.5 m.