Question

Two thin convex lenses \(A\) and \(B\) of focal lengths \(20\,\mathrm{cm}\) and \(30\,\mathrm{cm}\) respectively are placed coaxially in air with a separation between them. If an object is placed in front of lens \(A\) at a distance of \(45\,\mathrm{cm}\) from lens \(A\), the final image is formed at a distance of \(30\,\mathrm{cm}\) from lens \(B\). The distance between the two lenses is

• A. \(12\,\mathrm{cm}\)
• B. \(18\,\mathrm{cm}\)
• C. \(25\,\mathrm{cm}\)
• D. \(15\,\mathrm{cm}\)

Hint:

For two thin lenses, \[ \boxed{ \text{Image formed by the first lens acts as the object for the second lens.} } \] Apply the lens formula successively to each lens.

Answer 1

The Correct Option is C