Solving a Complex Problem: Can You Help?

[sfphysics]

Does anyone know how to solve this problem? I tried using the spherical interface formula (n1/p)+(n2/q)=((n2-n2)/R) and I get q=15cm which I cannot seem to relate to the answer provided (23cm). Anyone know the correct way to approach this problem?

Thanks.

 

[wukunlin]

You probably need to account for the flat end of the rod as well.

 

[SammyS]

Does anyone know how to solve this problem? I tried using the spherical interface formula (n1/p)+(n2/q)=((n2-n2)/R) and I get q=15cm which I cannot seem to relate to the answer provided (23cm). Anyone know the correct way to approach this problem?
[ IMG]https://www.physicsforums.com/attachment.php?attachmentid=58375&stc=1&d=1367371157[/PLAIN]

Thanks.

Is this a Homework problem?