Chapter 23 - Light: Geometric Optics

Ry Model of Light

A model that assumes light travels in stright lines called rays

Geometric Optics

The subject that studies the ray nature of light and how it interacts with objects

Angle of Incidence

The angle between a ray of light striking a surface and a line normal to the surface being hit

Angle of Reflection

The angle between a reflected light ray and a line normal to the surface being reflected

Law of Reflection

Angle of reflection equals angle of incidence

Diffuse Reflection

Occurs when light hits a rough surface and reflects in many directions since the angle of the surface is different across

Specular Reflection

Reflection on a mirror, light reflects at the same angles and will only hit your eyes at the right angle

Image

A reflection of objects in a mirror

Plane Mirror

A mirror with a single flat reflective surface

Image Point

The point from which a set of diverging rays appears to come from when an object is reflected in a mirror

Image Distance

The distance at which an image in a mirror appears to be from the mirror

Virtual Image

The image seen and reflected from a plane mirror

Real Image

An image where light passes through the image and can appear on a white surface, or on film

Spherical Mirror

A mirror whose surface is curved i the shape of a sphere or a section of one

Convex

Describes a spherical mirror where the reflective surface is on the outside of the spherical shape

Concave

Describes a spherical mirror where reflection takes place on the inside

Focus

The point at which rays that strike a concave mirror will cross

Principal Axis

The straight line perpendicular to the curved surface at its center, light rays mustbe parallel to this axis in order to have a focus

Focal Point

The point where reflected rays come to a focus

Focal Length

The length between the focal point and center of a concave mirror

Paraxial Rays

Rays that make small angles with the principal axis

Parabolic Reflector

A mirror shape that will reflect rays at a perfect focus

Object Distance

The distance an object is from the center of a spherical mirror, represented by do

Image Distance

The distance an object’s virtual image is from the center of a spherical mirror, represented by di

Mirror Equation

Relates the object and image distances to the focal length

Magnification

Defined as the height of the image divided by the height of the object

Focal Length

The distance an focal point is from the center of the mirror

Index of Refraction

The ratio between the speed of light in a vacuum and a given material, never less than 1

Refraction

The change in direction of a light ray due to it entering a new medium

Law of Refraction

Also called Snell’s law, used to relate the angles of incidence and refraction in optics

Critical Angle

The angle of incidence at which this occurs

Total Internal Reflection

Occurs when all light is reflected back into the medium it originatedfrom, can only occurs when n2 < n1

Fiber-Optic Cable

A bundle of plastic or blass fibers that use total internal reflection to transmit signals in the form of light

Converging Lens

A lens that is thicker in the center than at its edges, they focuses light

Diverging Lens

A lens that is thinner in the center than at its edges, they spread light out

Diopeter

A unit for lens power, defined as the inverse of a meter

Real Image

Formed by a double convex lens, since rays actually pass through the image

Thin Lens Equaiton

Relates image distance to object distance and focal length

Magnification

Same as the magnification of a mirror

Lensmaker’s Equation

Relates focal length of a lens to its radii of curvature, and index of refraction