Lesson 4 Define the terms principal axis, focal point, focal length and linear magnification as applied to a converging (convex) lens. Define the power. - ppt download
What Is Focal Length in Photography?
How To Define the Focal Point of a Room | Pella Windows & Doors
Define focal length.
Definition: Focal point; principle focus; point of interest - Photokonnexion
Focal points and focal planes, explained by RP; Gaussian optics