A concave convex figure lens made of glas `(mu=1.5)` has surface of radii 20 cm and 60 cm. a. Locate the image ofan object placed 80 cm to the left of the lens along the principal axis. B. A similar lens is placed coaxially at distanc of 160 cm right of it. Locate the position of the image.

Explanation

The focal length of the lens is given by
`1/f=(mu-1)(1/R_1-1/R_2)`
`=(1.5-1)(1/(20cm)-1/(60 cm))=1/(60cm)`
or `f=60 cm
a. for the image formed by lens `u=-80` cm so that
`1/v=1/u+1/f`
`=1/(-80cm)+1/(60cm)=1/(240cm)`
or `v=240 cm`
The first image `I_1` would form 240 cm to the right of the first lens. b. The second lens intercepts the converging beam as suggest by the ure. the image `I_1` acts as a virtual source of the second lens. For the image formed by this lens `u=240cm-160cm=+80` cm so that
`1/v=1/u+1/f`
` =1/(80cm)+1/(60cm)=7/(240cm)`
or `v=34.3cm`
the fiN/Al image is formed 34.3 cm to the right of the second lens.