Question: A lens has a power of +5 diopters. What is its focal length?
Options:
20 cm
25 cm
30 cm
15 cm
Correct Answer: 20 cm
Solution:
Power (P) = 1/f (in meters). Therefore, f = 1/P = 1/5 = 0.2 m = 20 cm.
A lens has a power of +5 diopters. What is its focal length?
Practice Questions
Q1
A lens has a power of +5 diopters. What is its focal length?
20 cm
25 cm
30 cm
15 cm
Questions & Step-by-Step Solutions
A lens has a power of +5 diopters. What is its focal length?
Step 1: Understand that the power of a lens (P) is related to its focal length (f).
Step 2: Remember the formula that connects power and focal length: P = 1/f.
Step 3: Rearrange the formula to find the focal length: f = 1/P.
Step 4: Substitute the given power into the formula: f = 1/5.
Step 5: Calculate the focal length: f = 0.2 meters.
Step 6: Convert meters to centimeters if needed: 0.2 meters = 20 centimeters.
Lens Power and Focal Length – The relationship between the power of a lens and its focal length, where power is the reciprocal of the focal length in meters.
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