Answer:
Optical axis
Step-by-step explanation:
Optical axis is the rotational symmetry axis of the surfaces.
A line with a certain degree of rotational symmetry is called as the optical axis in an optical system.
It is the straight line that passes through the geometric center of the lens and joins two curvature centers of its surfaces.
It is also called as the principal axis.
Answer:

Step-by-step explanation:
The circumference of a circle can be found using the following formula:

where d is the diameter. We know the diameter of the circle is 22 centimeters. Substitute the value in for d.


We also know we are using 3.14 for pi. Substitute it in for pi.

Multiply.

The circumference of the circle is 69.08 centimeters.
Integers I believe :) hope this helps