How would you draw a principal axis for a concave mirror?

To draw the principal axis for a concave mirror, start by sketching a horizontal line that represents the principal axis. Then, draw the concave mirror as a curved line facing the incoming light, with the reflective surface on the inside of the curve. Mark the focal point (F) on the principal axis at a distance equal to the focal length from the mirror's surface, and indicate the center of curvature (C) at twice that distance (2F) from the mirror. This principal axis is essential for understanding how light rays reflect off the mirror.