please help with trainee DO course

**NicolaKirk** · 10-13-2008, 09:13 AM

please can you help :hammer:

I'm currently stuck on a couple of questions

A -5.00D lenses is to be made in glass of refractive index 1.802, using tools calibrated for glass of refractive index 1.523. The tool marked +3.50 is used to work the front surface. Assuming that the tools step in 0.12D intervals, what tool would be selected to work the back surface?

Next:hammer:

A spherical generator is used to produce a -15.00Dsurface on glass of refractive index 1.80. The diameter of the cutting tool is 80mm and the radius of the cutting surface is 4mm. What is the angle between the axis of the tool and the axis of the lens?

I hope you can see my dilemma!!

Thanx Nicola :o

**HarryChiling** · 10-13-2008, 10:20 AM

For the tool problem check this thread out:

http://www.optiboard.com/forums/show...t=angle+cutter

There was also an image posted some time back showing the relationship, I would suggest doign a few searches, but the above posts has the direct equations you would need to solve your problem.

The tool marked as +3.50 in idex 1.523 should be converted first to the materials index.

D_1.802 = [(n_1.802 - 1) / (n_1.523 - 1)] * D_1.523
D_1.802 = 1.533 * +3.50
D_1.802 = 5.37

Now run it through the lensmakers equation:

D = F₁ + F₂
F₂ = D - F₁
F₂ = -5.00 - (5.37)
F₂ = -10.37

Now convert it back to the tool index:

D_1.523 = [(n_1.523 - 1) / (n_1.802 - 1)] * D_1.802
D_1.523 = 0.652 * (-10.37)
D_1.523 = -6.76

Now round that tool to 6.75D and your set to go.

Is this for the SMC course? Next time post these questions in the Ophthalmic Optics section, they'll get answered a lot quicker and by a few more people. Basicaly you'll be swimming in answers. :cheers:

**NicolaKirk** · 10-13-2008, 11:04 AM

Hi Harry, I'm Nicola from the uk, where are you from? Thank you for your help and advise it's greatly appreciated this is my first year. I'm training with ABDO (Association of Brittish Dispensing Opticians). I'm also just gettin used to the optiboard hope to speak with you again. :cheers:

Nicola :)

**HarryChiling** · 10-13-2008, 11:06 AM

Originally Posted by NicolaKirk

Hi Harry, I'm Nicola from the uk, where are you from? Thank you for your help and advise it's greatly appreciated this is my first year. I'm training with ABDO (Association of Brittish Dispensing Opticians). I'm also just gettin used to the optiboard hope to speak with you again. :cheers:

Nicola :)

US the ABDO program is a tough one from what I have heard and the quality optician that graduates is definately worthy of practiceing anywhere in the world. Good luck with your program and I'm sure as more questions come up we'll have other opportunities speak.