SH 402 · Chapter 5
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Two thin converging lenses of focal lengths $30\,\mathrm{cm}$ and $40\,\mathrm{cm}$ respectively are placed co-axially in air separated by a distance of $20\,\mathrm{cm}$. An object is placed $40\,\mathrm{cm}$ in front of the first lens. Find the position and nature of the image.
Two lenses of focal lengths $8\,\mathrm{cm}$ each are identical and co-axially separated by $4\,\mathrm{cm}$. Determine the equivalent focal length of the combination. If the image is formed at infinity at a particular position of the object, find the object distance.
Derive the expression for the equivalent focal length of two thin lenses having focal lengths $f_{1}$ and $f_{2}$ separated by a finite distance. Also find the expression for equivalent power.