Free ABO NOCE Question and Answers

Question 1

You can change a lens' focal length by:

Accepted Answer

Changing the curvature of one surface

Answer

The focal length of a lens is directly related to its optical power, which is determined by the refractive index of the lens material and the curvature of its surfaces. By altering the curvature of one or both surfaces, the degree to which light rays are converged or diverged changes. This modification directly impacts the lens's focal length, allowing for precise optical correction.

Question 2

Meniscus, equiconcave, and flat concave are varieties of

Accepted Answer

Minus lenses

Answer

Meniscus, equiconcave, and flat concave (or plano-concave) are all types of concave lenses. Concave lenses are thinner in the center and thicker at the edges, causing light rays to diverge. These lenses are used to correct myopia (nearsightedness) and are therefore classified as minus lenses, having negative dioptric power.

Question 3

What sort of lens has a surface that is both convex and concave?

Accepted Answer

Meniscus

Answer

A meniscus lens is characterized by having one convex surface and one concave surface. This design allows for better optical performance, reduced peripheral aberrations, and a thinner, more aesthetically pleasing lens, especially for higher prescriptions. Most modern spectacle lenses are manufactured with a meniscus shape.

Question 4

A lens's power is indicated by the word "axis."

Accepted Answer

False

Answer

The 'axis' in an eyeglass prescription refers to the orientation of the cylinder power, which corrects astigmatism. It indicates the meridian of the lens that has no cylinder power, or where the cylinder power is oriented. The lens's overall power (sphere and cylinder) is measured in diopters, not by the axis, which is an angular measurement.

Question 5

What word best describes the direction change of light as it moves from one medium to another?

Accepted Answer

Refraction

Answer

Refraction is the phenomenon where light changes direction, or bends, as it passes from one transparent medium into another with a different optical density. This bending of light is fundamental to how lenses work, allowing them to focus or diverge light rays to form images on the retina. Reflection, in contrast, is when light bounces off a surface.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

Free ABO NOCE Question and Answers