In a double convex lens, if the focal length is 15 cm, what is the power of the

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Question: In a double convex lens, if the focal length is 15 cm, what is the power of the lens? (2022)

Options:

Correct Answer: +7.5 D

Exam Year: 2022

Solution:

Power (P) of a lens is given by P = 1/f (in meters). Here, f = 15 cm = 0.15 m, so P = 1/0.15 = +6.67 D.

In a double convex lens, if the focal length is 15 cm, what is the power of the lens? (2022)

In a double convex lens, if the focal length is 15 cm, what is the power of the lens? (2022)

Step 1: Understand that the power of a lens is calculated using the formula P = 1/f, where P is the power in diopters (D) and f is the focal length in meters.
Step 2: Convert the focal length from centimeters to meters. Since the focal length is given as 15 cm, we convert it to meters by dividing by 100. So, 15 cm = 15/100 = 0.15 m.
Step 3: Substitute the focal length in meters into the power formula. We have P = 1/f, so P = 1/0.15.
Step 4: Calculate the value of P. When you divide 1 by 0.15, you get approximately 6.67.
Step 5: Since the lens is a double convex lens, the power is positive. Therefore, the final answer is +6.67 D.

Lens Power Calculation – Understanding how to calculate the power of a lens using its focal length.
Unit Conversion – Converting focal length from centimeters to meters before applying the formula.