Find the Image of a Point Object at a Glass Sphere

[pardesi]

Homework Statement

An object is kept at a distance d=2.5cm from a Glass sphere of radii R=10 cm .Find the final image of the point object?

$$\mu =1.5$$

Homework Equations

$$\frac{\mu_{2}}{v}-\frac{\mu_{1}}{u}=\frac{\mu_{2}-\mu_{1}}{R}$$

The Attempt at a Solution

it is a simple question where we have two interfaces and we have to calculate the image due to 1st surface which acts as object for second and then the final image.
But i am not getting the answer

 

[rl.bhat]

Show your calculations. What is your answer? What are the values of refractive indices

 

[pardesi]

the answer is 15cm in front of mirror
attempt being
for the first case object distance is -2.5cm and R.I is 1.5 plugging in the formulae i get
the image distance is v=-30/7
so this ats as image for 2nd surface and bject distance being u=-170/7=-30/7-20

again putiing in the values gives v=-85 cm which is far from the answer i don't get what i did wrong

 

[Shooting Star]

An object is kept at a distance d=2.5cm from a sphere of radii R=10 cm .Find the final image of the point object?

The Attempt at a Solution

it is a simple question where we have two interfaces and we have to calculate the image due to 1st surface which acts as object for second and then the final image.
But i am not getting the answer

The problem, as stated in the first para, presumably talks about a mirror. The attempt at solution talks about interfaces and RIs. Would you formulate the problem clearly?

 

[pardesi]

sorry it is a GLass SPhere