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  • A convex lens is placed on a stand, and an object is placed at a distance of from the lens. The obser

A convex lens is placed on a stand, and an object is placed at a distance of u = 20 cm from the lens. The observer looks at the object’s image formed by the lens, which appears to be at a distance v = 30 cm on the other side of the lens. Determine the focal length f of the convex lens using the lens formula.

Option: 1

0.6 cm


Option: 2

1.2 cm


Option: 3

1.8 cm


Option: 4

12 cm


Answers (1)

Step 1: Use the lens formula to relate the object distance (u), image distance (v), and the focal length (f) of the lens.

            \frac{1}{f}=\frac{1}{u}+\frac{1}{v}

Step 2: Solve the lens formula for the focal length (f).

            \frac{1}{f}=\frac{v+u}{uv}

            f=\frac{uv}{v+u}=\frac{20\times30}{20+30}=12 cm

So, the focal length (f) of the convex lens is 12 cm.
Therefore, the correct answer is D.

Posted by

Kshitij

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