Question

The formula for power of a lens is:

• A. \( P = \frac{1}{f} \)
• B. \( P = f \)
• C. \( P = \frac{1}{R} \)
• D. \( P = \frac{100}{f_{\text{cm}}} \)

Hint:

For lenses with focal length in centimeters, use \( P = \frac{100}{f_{\text{cm}}} \) to find the power in diopters.

Answer 1

The Correct Option is D

Step 1: Formula for Power of a Lens.
The power \( P \) of a lens is given by the reciprocal of the focal length \( f \), and if the focal length is measured in centimeters, then the formula for the power becomes: \[ P = \frac{100}{f_{\text{cm}}} \] where \( f_{\text{cm}} \) is the focal length in centimeters and the unit of power is diopters (D). Step 2: Conclusion.
Thus, when the focal length is given in centimeters, the power of the lens is calculated as \( P = \frac{100}{f_{\text{cm}}} \), where \( f_{\text{cm}} \) is the focal length in centimeters.