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.

Answer

A, B, C, D

Explanation

Image formed by lens t
`1/v_1-1/u=1/f`
`rarr 1/v_1=1/f+1/u`
`1/v_1=1/10-1/15`
`rarr v_1=30 cm `
`h_i/h_0=v/u`
h_i=-(5xx30)/15`
`h_i=-10mm

this will be object for lens II.
for II lens `u=-(40-30)`
`=-10cm`
`f=5cm`
`1/v-2=1/f+1/u`
`1/v_2=1/10`
`rarr 1/v_2=1/5-1/10`
`rarr v_2=10 cm (from IInd lens)`
h_(fiN/Al)/h_i=10/(-10)=h_(fiN/Al)`
`=h_i=10mm`
so image will be errect real and length =10 mm