Can you point me in the right direction
Hi Daryl,
I am new to Optiboard and currently studying to take the Advanced ABO exam in November. I am trying to figure out what to study to be able to answer queston 4, 8 and 19. Forgive me for asking something that is probably so obvious. I tried to figure out it out on my own...no luck.
Quote:
Originally Posted by
Darryl Meister
Practice Master Exam...
4. If your lens measure reads +6.00 D while measuring the front curve of a 1.66 high-index plastic lens, what is the actual refractive power of the lens surface?
8. An object 50 cm in front of a +5.00 D lens will come to a focus at what distance from the lens?
19. What is the focal length of a +5.00 D lens?
Which principals or formulas
Quote:
Originally Posted by
optin
Hi Daryl,
I am new to Optiboard and currently studying to take the Advanced ABO exam in November. I am trying to figure out what to study to be able to answer queston 4, 8 and 19. Forgive me for asking something that is probably so obvious. I tried to figure out it out on my own...no luck.
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Hi again thank you for the feedback; can you narrow it down for me a little. For example; to get the distance that the image will be if the object is 50cm in front of a +5.00 diopter lens; would I use the 1/f = 1/p + 1/q where f = focal length, p = object and q = image
By the way I have read all of your Opti campus courses and some that I found on line that you did for Zeiss. Actually I should say that I have read them over and over because there is alot to comprehend. I woke up one day and decided that if I am an Optician then I should understand the visual system and how a lens affects vision. It is way to easy to just fill an order. I really want to understand what is happening in the eye and when I put a lens in front of it. So I will get this all down; probably never to the extent of someone like yourself. I appreciate anything that can shorten the learning curve especially since I committed myself to this Advanced Test.
I figured out #19 forgot to convert to cm, please tell me the formula to determne refractive surface power if the know variable are D+6.00 and n=1.66
Best Regards and Thank You
Review materials for Advanced Exam
Quote:
Originally Posted by
Darryl Meister
Using the common optical sign convention, you can solve this problem using the following equation, known as the Conjugate Foci formula:
Or, substituting the reciprocal object (
l) and image (
l') distances for the vergences,
where
l is equal to -0.50 m, since the object is 50 cm in front of the wearer, and
l' is equal to +0.333 m, which is 33.3 cm behind the lens. Note that your equation is also the Conjugate Foci formula, but based upon a different sign convention.
Since the lens measure or lens clock is typically calibrated to a refractive index of 1.530, known as the "tooling" index, you can solve this problem using the following equation to convert surface power from the tooling index to the actual refractive index of the lens material, assuming that the actual physical curvature hasn't changed:
where
FREADING is the reading of 6.00 from the lens measure and the refractive index
n is 1.66.
Best regards,
Darryl
I took this formula from the NAO Math Review book and no-where is it refered to as the conjugate foci formula nor is there any reference to it in the NAO Advanced Opticians Tutorial. Your Ray Tracing C.E. course at the Opti Campus site makes it very clear.
http://www.opticampus.com/cecourse.php?url=ray_tracing/
I have ordered Ellen Stoners Optical Formulas Tutorial hopefully it is referenced there and with the common sign convention. I just want to understand how to evaluate and solve the requirement or problems and which formula gets the job done. Otherwise I will be thrown when I take the test and the same terminology or sign convention is not used. I am putting these comments on because I assume that others who plan to sit for the Advanced Exam will find value here. The Advanced Opticians Tutorial is a fine review source for everything but geometric optics and lens design. If the optical formulas tutorial by Stoner is not sufficient then I will order the Opthalmic Guide to Dispensing since it receives high reviews. I have been avoiding spending the money and yet I have wasted almost as much on these other sources.