Notes 23.3: Lenses and Images

Ray Diagrams for Pinholes: Object- real physical thing that gives off or reflects light Pinhole and Screen Light ray – straight line arrow that represents a single “beam” of light. (need 2 rays) Image – “picture” of the object that is formed where the rays land on the screen

Two types of Images: Virtual Image- image is perceived by the brain and eye as being some place that the light does not come from. Ex: image in a plane mirror is behind the mirror Real image – images are formed where the light rays actually come together; can be projected on a screen. Ex: pinhole, camera

Two Types of Lenses: 1. Converging lens – bends the light rays together so they meet at a single point. Ex: magnifying glass Also called convex, they are thicker in the middle than at the edges

Focal point – the point where parallel light meets when in travels through a lens. Focal Length – distance from center of the lens to the focal point. (measured in cm, m)

2. Diverging lens – bends light outward away from the optic axis. Ex: Some eye glasses Also called a concave lens, it is thinner in the middle than at the edges.

Ray diagrams for lenses will have: An object At least two light rays (we will draw three) Optic axis – imaginary line going through the center of the lens Two focal points on each side of the lens. An image (may be real or virtual)