Fixed Phong shading

Here are the results with the fixed Phong shading:
Index of refraction 1.33, camera farther:

Index of refraction 1.33, camera closer:

Index of refraction 2.69, camera farther:

Index of refraction 2.69, camera closer:

I don't like the amount of noise in these images. There are 512 samples per pixel. A relatively lame sample selection process is being used: lay them all out on a regular grid and use a random number generator to jitter the samples within their grid boundaries. This doesn't seem to be any better than simply choosing 512 pixels laid out on a regular grid.