# Homework Help: Mirror with 2 different radii

1. Mar 23, 2005

### Jacob87411

A piece of glas has an index of refraction of 1.5. The ends are hemispheres with radii 2 cm and 4 cm, and the distance that seperates the centers of the hemispherical ends. A point object is located in air 1 cm from the left end of the glass. Find the location of the image of the object due to refraction at the two spherical surfaces.

So on the left end the mirror has a radius of 2 cm, and on the right it is of 4 cm and the two are seperated by 8 cm.

Im thinking of using the equation: n2-n1/R = n1/d0 + n2/di. If so I will have to use it twice, one for each radius, which would give me two different di, then average them. Thats my thinking at least, not sure if its correct

2. Mar 23, 2005

### GCT

Tis a lens, not a mirror...mirror's don't refract.

Find the focal length using the maker's equation (or its derivative).

The rest should be simple.

Last edited: Mar 24, 2005
3. Mar 23, 2005

### Jacob87411

Ah..now i feel dumb

1/f = (n-1) (1/R1 - 1/R2)
n=1.5
R1=2
R2=4
Simple indeed, thanks