COMEDK · Physics · 25. Ray Optics
An object is placed at a distance of \(12 \mathrm{~cm}\) from a convex lens on its principal axis and a virtual image of certain size is formed. If the object is moved \(4 \mathrm{~cm}\) away from the lens, a real image of the same size as that of the virtual image is formed. The focal length of the lens in \(\mathrm{cm}\) is
- A 14
- B 16
- C 12
- D 18
Answer & Solution
Correct Answer
(A) 14
Step-by-step Solution
Detailed explanation
Let \(f\) be the focal length of the convex lens. The object distance is \(u_1 = -12 \text{ cm}\). The lens formula is \(\dfrac{1}{v_1} - \dfrac{1}{u_1} = \dfrac{1}{f}\). For the virtual image, the magnification is \(m_1 = \dfrac{v_1}{u_1} = \dfrac{v_1}{-12}\). Since the image…
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