Geometric Optics AP Physics Chapter 23

Geometric Optics 23.1 The Ray Model of Light

represents a narrow beam of light 23.1 The Ray Model of Light Light travels in a straight line in most cases (away from very large gravitational fields) Ray Model – Light travels in straight line pathways called rays represents a narrow beam of light 23.1

We see an object when rays of light come from the object to our eyes 23.1 The Ray Model of Light We see an object when rays of light come from the object to our eyes 23.1

23.2 Reflection: Image Formation by a Plane Mirror Geometric Optics 23.2 Reflection: Image Formation by a Plane Mirror

When light strikes an object it is Reflected – bounces off 23.2 Reflection When light strikes an object it is Reflected – bounces off Refracted – transmitted through Absorbed – converted to a different form of energy Law of Reflection 23.2

Diffuse Reflection – on a rough surface Rays don’t form an pattern We see color Specular Reflection – smooth surface Patterns form images 23.2

How are images formed Your eye sees the intersection of rays 23.2 Reflection How are images formed Your eye sees the intersection of rays from an object Applet 23.2

Object Distance – from mirror to the object 23.2 Reflection Object Distance – from mirror to the object Image Distance – from mirror to the image Virtual Image – imaginary intersection of light rays Real Image – actual intersection of light 23.2

23.3 Formation of Images by Spherical Mirrors Geometric Optics 23.3 Formation of Images by Spherical Mirrors

23.3 Formation of Images by Spherical Mirrors Spherical Mirrors – form a section of a sphere Convex – reflection on outer surface of sphere Concave – reflection on inner surface of sphere 23.3

23.3 Formation of Images by Spherical Mirrors Terms Principal Axis – straight line normal to the center of the curve Focus – point where parallel rays intersect Vertex – center of the mirror Focal Length – distance from vertex to focus Images from distant objects are produced at the focal point 23.3

23.3 Formation of Images by Spherical Mirrors The focal point is actually an approximation The greater the curve of a mirror, the worse is the approximation Called Spherical Aberration Examples of Visual Aberrations 23.3

23.3 Formation of Images by Spherical Mirrors All rays follow the law of reflection Two Rules A ray parallel to the principle axis reflects through the focal point A ray through the focal point reflects parallel Examples of Diagrams – Concave Mirrors Real Images Virtual Image 23.3

23.3 Formation of Images by Spherical Mirrors Convex Mirrors only form virtual images Rules Rays parallel to the principle axis reflect away from the focal point Rays headed for the focal point reflect parallel 23.3

23.3 Formation of Images by Spherical Mirrors Curved Mirror Equations ho-object height hi-image height do-object distance di-image distance The Mirror Equation Magnification 23.3

23.3 Formation of Images by Spherical Mirrors Sign Conventions Image Height + upright (virtual) - inverted (real) Image and Object Distance + front of mirror - behind mirror Magnification + upright image - inverted image 23.3

23.3 Formation of Images by Spherical Mirrors Sign Conventions Focal Length + concave mirror - convex mirror 23.3

Geometric Optics 23.4 Index of Refraction

23.4 Index of Refraction Index of Refraction – the ratio of the speed of light in a vacuum to the speed in a given material Material Index Vacuum 1.00000 NaCl 1.54 Air at STP 1.00029 Polystyrene 1.57 Water 1.33 Flint Glass 1.65 Quartz 1.46 Sapphire 1.77 Crown Glass 1.53 Diamond 2.417 23.4

Value can never be less than 1 23.4 Index of Refraction Value can never be less than 1 Material Index Vacuum 1.00000 NaCl 1.54 Air at STP 1.00029 Polystyrene 1.57 Water 1.33 Flint Glass 1.65 Quartz 1.46 Sapphire 1.77 Crown Glass 1.53 Diamond 2.417 23.4

23.5 Refraction: Snell’s Law Geometric Optics 23.5 Refraction: Snell’s Law

23.5 Refraction: Snell’s Law Refraction – when a ray of light changes direction as it changes media The change in angle depends on the change in velocity of light (or the index of refraction of the two media) 23.5

23.5 Refraction: Snell’s Law Snell’s Law – relates the index of refractions and the angles Also called the Law of Refraction If light speeds up, rays bend away from the normal If light slows down, rays bend toward the normal 23.5

23.5 Refraction: Snell’s Law Refraction occurs when one side of the wave slows down before the other 23.5

23.6 Total Internal Reflection; Fiber Optics Geometric Optics 23.6 Total Internal Reflection; Fiber Optics

23.6 Total Internal Reflection; Fiber Optics When light travels into a more optically dense medium, the ray bends away from the normal As the angle increases, the angle of refraction eventually reaches 90o. This is called the critical angle 23.6

23.6 Total Internal Reflection; Fiber Optics Above the critical angle, light reflects following the law of reflection Used in fiber optics 23.6

23.7 Thin Lenses; Ray Tracing Geometric Optics 23.7 Thin Lenses; Ray Tracing

23.7 Thin Lenses; Ray Tracing Thin lens – very thin compared to its diameter Diagrams are similar to mirrors Converging – rays converge 23.7

23.7 Thin Lenses; Ray Tracing Converging Lenses A ray parallel to the Principle Axis refracts through F A ray through F’ refracts parallel. A ray through the optical center, O, does not refract Converging Lens 23.7

23.7 Thin Lenses; Ray Tracing Diverging Lens – spreads apart rays of light Only produces virtual images Rules Parallel rays refract away from F’ Rays headed toward F refract parallel Rays through O do not refract 23.7

23.8 The Thin Lens Equation; Magnification Geometric Optics 23.8 The Thin Lens Equation; Magnification

23.8 The Thin Lens Equation: Magnification Equations are similar to Mirrors, conventions are different The Thin Lens Equation is To Calculate Magnification 23.8

23.8 The Thin Lens Equation: Magnification Conventions Focal Length + converging lens - diverging lens Object Distance + same side as original light - different side (only when more than 1 lens) 23.8

23.8 The Thin Lens Equation: Magnification Conventions Image Distance + opposite side from light - same side as light Height + upright - upside down 23.8

23.9 Combinations of Lenses Geometric Optics 23.9 Combinations of Lenses

23.9 Combinations of Lenses Many devices used combinations of lenses Combination problems are treated as separate lenses Calculate or draw the image from the first lens Applet 23.9