Image Formation and Physical Optics

Object vs Image  In this section we will be studying how mirrors and lenses will affect the way an object appears to us.  The thing that exists in the real world is referred to as the object.  The thing that we process through our eyes and brains is the image.  Real Image – formed when lights rays actually converge.  Virtual Image – formed when light rays appear to converge.  Our brains don’t know the difference between a real and virtual image!

Images  Everything we see with our eyes is a reflection. Light bounces off the world around us and that bounced/reflected light enters our eyes.  To study optics, we need to simplify some things.  We are only looking at one object at a time (usually represented by an arrow).  Instead of looking at the millions of light rays that enter our eyes, we are using the 3 most important rays.  We are looking for three changes that can occur with an image:  Change in distance from the mirror/lens  Change in direction (looks upside down)  Change in height or magnification

Flat Mirrors  O – Object  I – Image  P – Object distance from mirror  Q – Image distance from mirror

Flat Mirrors  We would draw a flat mirror problem like this:  Flat mirrors always:  create virtual images.  has p = q.  has an image that is unmagnified and upright.  has an image that has a front-back reversal. Object Image p q

Spherical Mirrors  Spherical Mirrors are simply curved mirrors  C – Center of Curvature  R- Radius of Curvature  P – Principal Axis  f – Focal Point R

Curved Mirror Equations Magnification Height of Object Height of Image

Sign Conventions for Mirrors  Positive and negative signs are very important when solving for the image. +- preal object--- qreal image (in front of mirror) virtual image (behind mirror) hihi UprightInverted fConcave MirrorConvex Mirror

Concave Mirrors Ray 1 – Start straight, then reflect through focal point. Ray 2 – Start through the focal point, then reflect straight Ray 3 – Pass right through the center of curvature

Convex Mirrors Ray 1 – Start straight, then reflect through focal point. Ray 2 – Start through the focal point, then reflect straight Ray 3 – Pass right through the center of curvature

Lenses  Lenses are a transparent material that has a curve.  f – focal point  p – principal axis p

Lens Equations Index of Refraction Radius of Curvature for each side of lens

Sign Conventions for Lens  Positive and negative signs are very important when solving for the image. +- preal object--- qreal image (behind lens) virtual image (in front of lens) hihi UprightInverted fConverging LensDiverging Lens

Converging Lens Ray 1 – Start straight, then refract through focal point. Ray 2 – Start through the focal point, then refract straight. Ray 3 – Pass right through the center of the lens.

Diverging Lens Ray 1 – Start straight, then refract through focal point. Ray 2 – Start through the focal point, then refract straight. Ray 3 – Pass right through the center of the lens.