Chapter 14 Light & Reflection Physics

Light and Reflection ☺Electromagnetic Waves ☺Transverse Waves ☺Oscillating Electric and Magnetic Fields Perpendicular to Each Other

Light and Reflection ☺Sources of Light ☺Transparent ☺Materials that Transmit Light Waves without Distortion ☺Translucent ☺Materials that Transmit Light Waves with Some Distortion ☺Opaque ☺Materials that Do Not Transmit Light Waves ☺Instead, They Reflect Light Waves

Light and Reflection ☺Light ☺Range of Electromagnetic Frequencies ☺ 750nm – 380nm

Light and Reflection ☺Light ☺Travels in a Straight Line ☺Models Using Light “Rays” ☺Speed of Light ☺c ~ 3.00x10 8 m/s

Light and Reflection ☺Light ☺Wave Front ☺Point Source ☺Rays ☺Huygens’ Principle

Light and Reflection ☺Luminous ☺Emits Light Directly ☺Sun ☺Illuminated ☺Reflects Light ☺Moon

Light and Reflection ☺Luminous Flux (P) ☺Amount of Visible Light Emitted from a Source ☺Brightness ☺Units are Lumens ☺Illuminance (E) ☺The Rate of Illumination Provided by a Light Source ☺Lumens / m 2 ☺1 lumens/m 2 = 1 Lux

Light and Reflection ☺Luminous Intensity (cd) ☺Units are Candela (“Candle Power”) ☺Luminous Flux in an Area of 1m 2, 1m from a Source ☺Illuminance (E)

Light and Reflection ☺Increasing Illumination ☺Increase Luminous Flux ☺Use a Brighter Bulb ☺Decrease the Distance Between the Light Source and the Illuminated Surface

Light and Reflection ☺Inverse – Square Relationship ☺Luminous Flux in an Area of 1m 2, 1m from a Source ☺so… ☺At a Distance of 2m, the Area is 4m 2 ☺The Luminous Flux Stays the Same, so Illuminance Would be ¼ of the Original

Light and Reflection ☺Homework: ☺Page 550 ☺Problems: ☺10 ☺11 ☺12 (3.02 m) ☺13 (9.1mm)

Light and Reflection  Law of Reflection  “Normal to the Surface” (“Normal”)  A Line Perpendicular to a Reflective Surface  Incident Ray  Light Ray Striking a Reflective Surface from a Light Source  Reflected Ray  Light Ray Reflecting from an Incident Ray off a Reflective Surface

Light and Reflection  Law of Reflection  Incident Angle (Angle of Incidence)  The Angle Between the Incident Ray and Normal  Reflective Angle (Angle of Reflection)  The Angle Between the Reflected Ray and Normal

Light and Reflection  The Law of Reflection  Incident Angle (  i ) = Reflected Angle (  r )

Light and Reflection  Regular Reflection  Diffuse Reflection

Light and Reflection  Regular Reflection  Light is Reflected Back to the Observer in Parallel Rays Off a Smooth Surface  Diffuse Reflection  Light is Reflected Back to the Observer in a Wide Range of Angles Due to a Rough Reflective Surface

Light and Reflection  The Formation of Images by a Plane Mirror  Images are…  Upright  Equal Size  Image Distance from Media Surface is Equal to the Object Distance from the Media Surface  Reversed R to L

Light and Reflection  The Formation of Images by a Plane Mirror

Light and Reflection Real Image  Light Rays Converge and Pass Through the Image  Can Be Viewed on a Screen FC Real Image Object Ray 1 Ray 2

Light and Reflection Virtual Image  Light Rays Diverge from a Point Behind the Mirror  Rays of Light that Appear to be Reflected from the Virtual Image Actually are Reflected from the Object

Light and Reflection  The Formation of Images by Spherical Mirrors  Concave Mirror  R = Mirror Radius  C = Center of Radius  F = Focal Point FC R Principal Axis

Light and Reflection  The Formation of Images by Spherical Mirrors  Concave Mirror FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Concave Mirror  Ray Tracing  Object Position  Observer Position  Image Position FC Image Object Ray 1 Ray 2

Light and Reflection  The Formation of Images by Spherical Mirrors  Concave Mirror  Paraxial Rays  Light Rays Near, but not Necessarily Parallel to the Center Axis FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Concave Mirror  Spherical Aberration  Blurred Virtual Image  Caused by Rays Other than Paraxial Rays Converging on Points Other than the Focal Point  Small Diameter/Radius Ratio Helps Reduce SA FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Convex Mirror FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Convex Mirror FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Convex Mirror  Ray Tracing  Object Position  Observer Position  Image Position F Image Object Ray 1 Ray 2

Light and Reflection  The Formation of Images by Spherical Mirrors  Mirror Equation  f = Focal Length of the Mirror  d 0 = Distance Between the Object and the Mirror  d i = Distance Between the Image and the Mirror FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Magnification Equation  m = Magnification  h i = Image Height  h o = Object Height FC R

Light and Reflection  The Formation of Images by Spherical Mirrors  Conventions  Focal Length  + for Concave  - for Convex  d o  + for Real Object  - for Virtual Object

Light and Reflection  The Formation of Images by Spherical Mirrors  Conventions  d i  + for Real Image  - for Virtual Image  m  + for Upright Image  - for Inverted Image

Light and Reflection  Parabolic Mirrors  Eliminate Spherical Aberration

Light and Reflection ☺Homework: ☺Pages ☺Problems: ☺20 ☺34 ☺a, M=-0.384;real, inverted ☺b, M=-1.0;real, inverted ☺c, M=1.67;virtual, upright ☺35 (p = 13cm; real, inverted, M=-2.0) ☺36 (p = 53.5cm; h=5.76cm; virtual, upright, M=0.295)

Light and Reflection ☺Color ☺White Light is All Colors Combined ☺Some Colors Absorbed ☺Some Colors Reflected ☺The Color We See is the Color Reflected ☺ALL WE SEE IS REFLECTED LIGHT!

Light and Reflection ☺Colors by Addition (Mixing Light) ☺Primary Colors ☺Red ☺Green ☺Blue ☺Secondary Colors ☺Cyan – Complementary to Red ☺Magenta – Complementary to Green ☺Yellow – Complementary to Blue

Light and Reflection ☺Colors by Subtraction (Mixing Pigments/Filtering) ☺Primary Colors ☺Cyan ☺Magenta ☺Yellow ☺Secondary Colors ☺Red – Complementary to Cyan ☺Green – Complementary to Magenta ☺Blue – Complementary to Yellow

Light and Reflection ☺Colors by Subtraction ☺Dye ☺Molecule in Solution ☺Pigment ☺Compound in Suspension

Light and Reflection ☺Color ☺Polarization of Light ☺Alignment of Transverse Light Waves ☺Accomplished by Filters

Light and Reflection

☺Homework: ☺Pages 552 – 553 ☺Problems: ☺48 (-31.0cm) ☺51 (11.3cm) ☺55 (-25.0cm)