A thin lens has a focal length of 20 cm. What is the power of the lens?

A thin lens has a focal length of 20 cm. What is the power of the lens?

Step 1: Understand that the focal length (f) of the lens is given as 20 cm.
Step 2: Convert the focal length from centimeters to meters because the formula for power uses meters. 20 cm = 20/100 = 0.2 meters.
Step 3: Use the formula for power (P) of a lens, which is P = 1/f, where f is the focal length in meters.
Step 4: Substitute the value of f into the formula: P = 1/0.2.
Step 5: Calculate the power: P = 1/0.2 = 5.
Step 6: Since the lens is a thin lens, the power is positive, so we write it as +5 D (diopters).

Lens Power – The power of a lens is the reciprocal of its focal length measured in meters, expressed in diopters (D).