Question

a convex lens of focal lenght 10 cm is placed xoaxiaaly 5cm away from a concave lens of foacl length 10cm if the object is placed 30cm in front of the convex lens. find the position of the final image formed by the combines series.

Answer 1

$$\begin{gathered} f=10cm \\ u=-30cm \\ 1/f=1/v-1/u \\ 1/10=1/v+1/30 \\ v=15cmwrttoconvexlens. \\ ufortheconcavelens=15-5=10cm \\ nowforconcavelens: \\ 1/f=1/v-1/u \\ 1/-10=1/v-1/10 \\ v=\infty \end{gathered}$$