NOCE Lens Treatments and Coatings 2

Question 1

An uncoated standard CR-39 plastic lens reflects approximately what percentage of incident light from each surface?

Accepted Answer

8%

Answer

An uncoated CR-39 lens reflects approximately 4% per surface (front and back combined approximately 8%), which AR coatings reduce to under 1% total.

Question 2

Photochromic lenses typically activate in response to which type of radiation?

Accepted Answer

Ultraviolet (UV) radiation

Answer

Photochromic lenses are activated primarily by UV radiation, which triggers the reversible molecular change that causes darkening — this is why they often don't darken behind UV-blocking car windshields.

Question 3

What is the primary function of a hydrophobic coating applied over an anti-reflective coating?

Accepted Answer

To repel water, oils, and smudges from the lens surface

Answer

A hydrophobic (water-repelling) top coat causes water and oils to bead up and roll off the lens surface, reducing smudging and making the lens easier to clean.

Question 4

Which type of lens treatment is applied to create a reflective, mirror-like appearance on the front surface of sunglasses?

Accepted Answer

Flash or mirror coating deposited on the front surface

Answer

A flash or mirror coating is a vacuum-deposited metallic layer on the front surface that creates a reflective appearance while reducing visible light transmission.

Question 5

Blue light-filtering lenses are designed to reduce transmission of light in which approximate wavelength range?

Accepted Answer

380–500 nm (violet to blue visible light)

Answer

Blue light lenses target the 380–500nm range, which includes high-energy visible (HEV) blue-violet light associated with digital screens and linked to potential retinal and sleep-cycle concerns.

NOCE - National Opticianry Competency Examination Practice Test

NOCE - National Opticianry Competency Examination Practice Test

NOCE Lens Treatments and Coatings 2