NOCE Lens Treatments and Coatings 3

Question 1

What is the most common cause of crazing (a fine network of cracks) in anti-reflective coated lenses?

Accepted Answer

Thermal stress or chemical incompatibility causing the coating to separate from the lens substrate

Answer

Crazing occurs when the AR coating and lens substrate expand or contract at different rates due to heat or chemical exposure, causing the coating to crack and delaminate from the lens surface.

Question 2

Which lens treatment is most effective at eliminating glare from horizontal reflective surfaces such as water, snow, and wet roads?

Accepted Answer

Polarized filter integrated into the lens substrate

Answer

Polarized lenses contain a filter that blocks horizontally polarized light, which is the predominant orientation of glare reflected from flat horizontal surfaces.

Question 3

What is the purpose of applying an anti-reflective coating to the back (ocular) surface of prescription sunglass lenses?

Accepted Answer

To reduce reflections of light entering from behind that bounce off the back surface into the eye

Answer

A back-surface AR coating on sunglass lenses prevents light entering from behind and at angles from reflecting off the inner lens surface into the wearer's eye, which would negate some of the front tint's benefit.

Question 4

Which environmental factor most significantly reduces the darkening performance of standard photochromic lenses on a bright sunny day?

Accepted Answer

High ambient temperature

Answer

High ambient temperatures impede the molecular transition in photochromic materials, causing them to achieve a lighter final state than they would under cooler conditions with the same UV intensity.

Question 5

Compared to a standard single-layer AR coating, a premium multi-layer AR coating typically reduces surface reflection to approximately what level?

Accepted Answer

Less than 0.5% total reflection, compared to 2–4% for standard AR

Answer

Premium multi-layer AR coatings can reduce total surface reflection to below 0.5%, compared to standard AR coatings that may only reduce reflection to approximately 2–4%, significantly improving light transmission.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

NOCE Lens Treatments and Coatings 3