Chapter 13 Light and Reflection

Chapter 13 Light and Reflection 13-1 Electromagnetic waves Electromagnetic Waves  A wave that consists of oscillating electric and magnetic fields which radiate outward from the source at the speed of light  The spectrum includes o Radio waves, microwaves, infrared waves, visible light, ultraviolet light, X-rays, gamma rays  em waves are transverse waves  All em waves move at the speed of light: o 3 x 108 m/s (in a vacuum) o c = fλ o c: speed of light (m/s) 13-2 Flat Mirrors Reflection of Light  Light traveling through a uniform substance always travels in a straight line  When the light encounters a different substance its path will change: reflection o Some light will be absorbed, and the rest is deflected at the surface The texture of a surface affects how its reflects light  Diffuse reflection: light reflected from a rough, textured surface that is reflected in many different directions  Specular reflection: light reflected from smooth, shiny surfaces that is reflected in one direction only Incoming and reflected angles are equal  Angle of incidence: the angle between a ray that strikes a surface and the line perpendicular to that surface at the point of contact  Angle of reflection: angle formed by the line perpendicular to a surface and the direction in which a reflected ray moves  Angle of incidence = angle of reflection Flat Mirrors  Simplest mirror is a flat mirror  Object’s distance from the mirror is equal to the image’s distance from the mirror  The image of the object is the same size as the object  Produces virtual images: cannot be projected on a screen  The image formed appears reversed to an observer in front of the mirror Image location can be predicted with ray diagrams  Ray diagram: use simple geometry to locate an image formed by a mirror 13-3 Curved Mirrors Concave Spherical Mirrors  A mirror whose reflecting surface is a segment of the inside of a sphere  Can be used to form real images: an image formed by the intersection of light rays; can be projected on a screen Image location can be predicted with the mirror equation  Mirror Equation o 1/p + 1/q = 1/f o p: object distance o q: image distance o f: focal length  Distances have a positive sign when measured from the center of the mirror to any point on the mirror’s front side  Distances have a negative sign when measured to the mirror’s back side Magnification relates image and object sizes  M = h’/h = -q/p o h’: image height o h: object height o q: image distance o p: object distance  When M is + image is upright and virtual  When M is – image is inverted and real Ray Diagrams can be used for spherical mirrors 1. Draw line parallel to principal axis and then through focal point F 2.Draw line through focal point F and parallel to principal axis 3.Draw line through center of curvature

Convex Mirrors  A mirror whose reflecting surface is an outward-curved segment of a sphere  Creates virtual images  Magnification is always less than 1  Mirror is used to take objects in a large field of view and produce a small image