A 5 mm high pin is placed at a distance of 15 cm from a convex lens of focal length 10 cm. A second lens of focal length 5 cm is placed 40 cm from the first lens and 55 cm from the pin. Find (a) the position of the final image, (b) its nature and (c) its size.

Explanation

Image by first lens:
`(1)/(v_1)-(1)/(-15)=(1)/(10)implies(1)/(v_1)=(1)/(10)-(1)/(15)=(1)/(30)`
`v_1=30cm`
`(I_1)/(O)=(v_1)/(u_1)implies(I_1)/(5)=(30)/(-15)`
`I_1=-10mm`
Image by second lens :
At 10 cm on the other side of lens,inverted and of same size.
(a) 10 cm light of second lens
(b) real
(c) 10 mm