What will be the focal length of a convex lens with the power of a +2.5 Diopter?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 40 cm.
The power of a lens (P) is inversely proportional to its focal length (f) when the focal length is expressed in meters. The formula is given by:
P=1/f
Given the power (P) = +2.5 diopters.
To find the focal length (f) in meters:
f=1/P
f=1/2.5 meters
f=0.4 meters
To convert the focal length from meters to centimeters, multiply by 100:
f=0.4×100 cm
f=40 cm.