COT Optics and Lensometry 5

Question 1

Which aberration causes peripheral rays passing through a lens to focus at a different point than paraxial rays, reducing image sharpness?

Accepted Answer

Spherical aberration

Answer

Spherical aberration occurs because peripheral rays refract more than paraxial rays, creating multiple focal points along the axis.

Question 2

A concave (minus) lens causes light rays to:

Accepted Answer

Diverge as if coming from a virtual focal point

Answer

A concave lens diverges light, and the divergent rays appear to originate from a virtual focal point on the same side as the incoming light.

Question 3

When using the lensmeter to locate the optical center of a lens, what phenomenon indicates that you are centered on the optical center?

Accepted Answer

No prismatic displacement of the mire target

Answer

At the optical center, no prism is present, so the mire target is centered in the reticle without displacement.

Question 4

What is the recommended sequence for lensometry of a progressive addition lens?

Accepted Answer

Read distance zone first, then move to near zone to calculate add power

Answer

Standard procedure reads the distance power first from the upper portion, then the near power from the lower reading zone to calculate the add.

Question 5

Which law states that the angle of incidence equals the angle of reflection when light strikes a smooth surface?

Accepted Answer

The Law of Reflection

Answer

The Law of Reflection states that the angle of incidence equals the angle of reflection, both measured from the normal to the surface.

COT - Certified Ophthalmic Technician Practice Test