A point object is located at a distance of 15 cm, from the front surface of a thick bi-convex lens. The lens is 10 cm thick and radii of its front and back surfaces are 10 cm and 25 cm respectively. How fae beyond the back surface of this lens `(mu=1.5)` is the image formed?

Explanation

Here thickness of lens is given.
Refraction at (1):
`mu_1=1,mu=(3)/(2),u=-15cm,R=10cm,v=?`
`(mu_2)/(v)-(mu_1)/(u)=(mu_2-mu_1)/(R)`
`((3)/(2))/(v)-(1)/(-15)=((3)/(2)-1)/(10)implies(3)/(2v)+(1)/(15)=(1)/(20)`
`(3)/(2v)=(1)/(20)-(1)/(15)=-(1)/(60)`
`v=-90cm`
Refraction at (2):
`mu_1=(3)/(2),mu_2=1,u=-(90+10)=-100cm,R=-25cm,v=?`
`(1)/(v)-((3)/(2))/(-100)=(1-(3)/(2))/(-25)`
`(1)/(v)+(3)/(200)=(1)/(50)implies(1)/(v)=(1)/(50)-(3)/(50)-(3)/(200)=(1)/(200)`
`v=200cm`