Some findings
1. In the refraction texture we define, the variable called refractionratio of the material is actually the (refractive index of air/ refractive index of lens).
2. Then if we increase refractive index, refractionratio decreases. When refractionratio increases, the focal length also increases. So the behaviour of the lens and the refraction ratio is in accordance with the real world and the lens makers formula.
3. We can use any material with refractive index > 1 and we would get a good behaviour.
4. As the radius of curvature increases, the focal length increases as well.
5. When we put the object at a distance at less than the focal length we get no(virtual) image.

Progress.........

So here is what I have done so far with the lab and am stuck here thinking hard....

Features available
1. A proper environment to move about
2. An optic bench that has a scale to measure the values
3. The freedom to move the object and image pins along the optic bench using the slider in HTML
4. A lens that has dynamic cube mapping feature
5. Three modes
5.1 Prepare mode - You can see the whole room and make arrangement for the experiment
5.2 Inspect mode - Keeps the camera in position to check the lens views
5.3 Read mode - Helps you to take the readings easily from the scale
6. Facility to increase and decrease the refractive index - The value is available on the top in HTML

A free demo of the usage is below. Please visit the link
http://www.youtube.com/watch?v=mkJqHsOJHBw&feature=youtu.be

Why I ponder -
1. When the refractive index goes above 1, a rather strange thing happens
2. My doubt is that the focal length of the lens is dependent on the radius of curvature of the lens as well. Since the radius of curvature of the sphere used to build the lens has to be in same units as that in the scale of the environment, this can be the cause of the problem

The big problem - The units, it is really a headache. If I make a cube of side 2 in Blender, is it the same units in the three.js. If not then we will not get accurate values for measurements.
Onto this now........................