ABO NOCE Basic Opticianry Ophthalmic Optics and Principles 2

Question 1

Which lens form has the same power on both surfaces but with one surface convex and the other concave?

Accepted Answer

Meniscus

Answer

A meniscus lens has one convex and one concave surface, giving it a crescent-like cross-section.

Question 2

What is the term for the bending of light as it passes from one medium to another of different optical density?

Accepted Answer

Refraction

Answer

Refraction is the change in direction of light as it crosses the boundary between two media with different indices of refraction.

Question 3

If a lens has a back vertex power of +3.00 D and a front vertex power of +2.75 D, which power is used when verifying the prescription with a lensometer?

Accepted Answer

Back vertex power

Answer

The back vertex power is the standard used for lensometer verification because it represents the effective power at the back surface closest to the eye.

Question 4

What happens to the critical angle when light travels from glass (n=1.5) into air (n=1.0)?

Accepted Answer

It is approximately 41.8°

Answer

Using sin(c) = n2/n1 = 1.0/1.5, the critical angle for glass-to-air is approximately 41.8°.

Question 5

A prism with apex angle 10° and refractive index 1.5 produces approximately how much deviation in diopters (prism diopters)?

Accepted Answer

10Δ

Answer

Prentice's approximation: P = a(n-1) × 100, so 10 × 0.5 = 5°, but in prism diopters at thin prism approximation, deviation ≈ 10Δ for an apex of 10° with n=1.5.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Ophthalmic Optics and Principles 2