# Homework Help: Images by refraction problem

1. Dec 7, 2009

### bodensee9

1. The problem statement, all variables and given/known data
Hello: I am wondering if someone can help with the following?
A rod that is 96 cm long is made of glass with index of refraction of 1.6. The rod has its end ground to convex spherical surfaces with radii of 8 cm and 16 cm. An object is in air on the long axis of the rod 20 cm from the end with the 8 cm radius. Find the image distance due to refraction at the 8 cm surface. Find also the position of the final image due to refraction at both surface.

3. The attempt at a solution

I know the first one. I will have: 1/20 + 1.6/s = (1.6-1)/8. So then I get 64 cm. This means that the image of the object is 64 cm inside the glass tube. I am not sure about the second one. I know that the image from the 8 cm mirror will serve as the object for the 16 cm mirror. So then do I have that the image from the 8 cm mirror is (96-64) from the end of the 16 cm mirror? I am not sure about the signs. I know that distance is positive if it is on the light incident side. So would distance from the image of 8 cm to the radius of the 16 cm mirror be negative because the light incident side would come from the outside of the glass tube? And wouldn't the indices of refraction be the same? Since the equation is n1/s1+n2/s2 = (n2-n1)/r. Would I have 1.6/32 + 1/s2 = (-.6)/16? I think the image of the 16cm will be on the outside of the glass tube. Thanks