(electronic sounds)
(introductory music)
- Hello, I'd like to welcome you to the Laramy-K
Optician Works Training Center,
where last week I used the dreaded p word.
I also said that an eyeglass lens is nothing more or less
than a piece of curved plastic.
And this week, I want to talk just a little tiny bit more
about those curves.
An excellent place to start this is
the Laramy-K Optician Works mantra.
The shorter the radius, the steeper the curve.
The steeper the curve, the higher the power.
The higher the power, the thicker the lens
in a given material.
It will never let you down.
You should already have that memorized
and these concepts should already be familiar to you.
But let's take a brief sidestep.
I have two lenses.
I have a blue lens and a red lens.
My blue lens, low power
because it has a very shallow radius of curvature.
It has a radius of 330 millimeters and this is actual,
this is actually 330 millimeter radius about there.
Okay, and so I drew this.
Very shallow, it only has the power of 1.61.
My red has an extremely short radius of curvature,
83 millimeters.
And this material, it gives me a power of six,
much, much stronger but they are of the exact
same equal blank size.
The cord, this plano line that we'd cut out
and removed as a lens.
They're exactly the same, right here,
right here, right here.
They're my two lenses,
both working from the same diameter,
because the steeper radius, stronger power.
Again, you kind of should be familiar with that.
What we're going towards here is the surface power formula
where we can solve for the radius,
or the power when we know our index.
Now, what the big takeaway from this is,
is that power is related to curvature,
the curvature is related to power.
The power of an eyeglass lens comes from its curves,
and material.
A lens is not a pill.
Let's break these two lenses out, redraw them
and work the surface power formula
to solve for the radius and to solve for power.
All right, we have our two lenses
that we had literally just popped out of the other drawing.
Here's our shallow weak little blue
with the big long radius of curvature.
Here's our red is steep, powerful lens.
Remember, of course that material matters.
So we're going to be given in our index of refraction
for the material depending on the material,
light will slow down and change direction more.
So, it's going to influence overall power.
1.53 Tridex, Crown Glass.
1.498 CR-39.
So material matters here,
I can use the surface power formula
to solve for either the power of the lens
or the radius of curvature of the curve
that I'd required in order to create to the power necessary.
For instance, if I want to solve for power,
I'm given n and I'm given the radius of this
curve in meters, 0.33, third of the meter.
Then that is actually again, correct.
D is equal to 1.53 minus one divided by 0.33.
0.53 divided by 0.33 is 1.61.
The power of a lens with a front radius of 0.3 meters
and a Plano backside, pop it into the lens meter,
that is what you're gonna get.
Direct relationship between radius of curvature and power.
If I need to work it the other way and solve for radius,
n is equal to 1.498,
D six.
1. 498 minus one divided by 6.
0.498 divided by six tells me
that the radius of curvature for this
is a tiny little short, we just saw this
I just showed it to you 0.083, meters,
or in other words 83 millimeter.
And that is that.
If you're watching me on YouTube,
please go ahead and hit that subscribe button
down there in the corner,
watching me on Facebook, give us a like.
Please make sure that every lens
regardless of its power or curvature comes from Laramy-K,
I will see you again next week.
The shorter the radius, the steeper the curve,
the steeper the curve...
(laughs)
(beep)
(upbeat music)