ABO NOCE Basic Opticianry Ophthalmic Optics 3

Question 1

What is the focal length of a +2.50 D lens?

Accepted Answer

40 cm

Answer

Focal length (in meters) = 1 / power, so 1 / 2.50 = 0.40 m = 40 cm.

Question 2

Chromatic aberration in lenses is caused by:

Accepted Answer

Different wavelengths of light being refracted at different angles

Answer

Different wavelengths (colors) of light have different refractive indices in a material, causing them to focus at slightly different points — this is chromatic aberration.

Question 3

Which lens form has the least peripheral distortion for most prescriptions?

Accepted Answer

Best form (corrected curve)

Answer

Best form (corrected curve or best-form) lenses are designed with specific base curves that minimize oblique astigmatism and peripheral distortion.

Question 4

The critical angle for total internal reflection depends on:

Accepted Answer

The refractive indices of both media at the interface

Answer

The critical angle is determined by sin(θc) = n2/n1, so it depends on the refractive indices of both the dense and less-dense media at the interface.

Question 5

Oblique astigmatism in ophthalmic lenses is an example of which type of lens aberration?

Accepted Answer

Monochromatic (Seidel) aberration

Answer

Oblique astigmatism is one of the five classic Seidel (monochromatic) aberrations that affect the quality of images formed by lenses.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Ophthalmic Optics 3