Presentation on theme: "Chapter 7:Understanding Light"— Presentation transcript:
1 Chapter 7:Understanding Light Topic 7.1: What is Light?Topic 7.2: Reflecting on ReflectionsTopic 7.3:Refraction
2 Topic: What is Light? A.The First Property of Light Light is a form of energy.There are natural light sources: sun,fire,stars.
3 A.The First Property of Light: Energy can change forms- from natural to artificial.Ex. Solar to thermal. Ex. Solar to chemical.Ex. Solar to electrical
4 A. Light: cont’dArtificial light sources: light bulb, match (chemical), a flashlight (electrical)Thomas Edison ( )
5 B. Sources of Light: 1. Incandescent Incandescent light source: they are so hot they glow.Ex. Light bulbs.Electrical energy is converted into 95% thermal energy and 5% light energy
6 2. LuminescentLuminescent light: does not need to be hot to create light.The following, (a)-(d), are all types of luminescent light sources.
7 a) Fluorescent light: Ex. Fluorescent light bulb. Advantage: does not waste energy as heat (is more energy efficient.)Disadvantage: Filled with mercury (Hg) and phosphorus (P) , both toxic chemicals
8 b) Phosphorescent light: Ex. Glow in the dark items.Particles absorb light (radiant) NRG and store it for a time.
9 c) Chemiluminescent light source: Ex. Glow sticksLight energy released from a reaction between two chemicals.
10 d) Bioluminescent light Source: Ex. Fire fliesChemical reactions in a living organism provide energy for light.
11 Examples of bioluminescence Bioluminescent mushroomsMicroscopic organism- white spot on the left is the bioluminescence
12 C. WattThe Watt: is the unit of electrical power(W). It indicates the rate at which energy is consumed.1000 watts= a kilowatt (kW)Kilowatt-hour is the amount of electrical NRG used in one hour.(kW•h)James Watt ( )
14 D. Second Basic Property of Light: Light travels in a straight line.A ray diagram is used to show the direction in which light is traveling.
15 D. Light travels in a straight line Sun rays through clouds, and shining down into a gorge.
16 D. Light travels in a straight line. Light travels in a straight line until the light strikes an object or material.The material can be opaque: that is not let any light pass through it.Ex. wood, metal.
17 D. Light travels in a straight line The material can be translucent: Some light passes through it and it is scattered.Ex. Frosted glass, wax paper, stained glass.
18 D. Light travels in a straight line. The material can be transparent: All light passes through freely.Ex. Glass.
20 Topic 7-2: Reflecting on Reflections Reflection occurs when light bounces off a surface.If the surface is smooth, a clear image is produced.If the surface is rough, a diffuse reflection results.
21 A. Laws of Reflection First Law of Reflection: The Angle of incidence is equal to the angle ofreflection.
22 A. Laws of Reflection Second Law of reflection: The incident ray, the reflected ray and thenormal are all in thesame plane.This supports the second basic property of light.
23 B. Optical IllusionMan playing a horn or silhouette of a woman?Optical illusions fool our brain into making false conclusions.And they’re lots of fun!Wine glass or 2 people?
24 C. Predictable Behavior of Light Light rays will either be :AbsorbedReflectedRefractedReflection: Occurs when light hits a smooth shiny surface and “bounces” off.EX. mirror“Smooth as glass…”
25 C. Predictable Behavior-Reflection All of the light that reaches a plane(flat) mirror is reflected.
26 C. Predictable Behavior-Reflection This will produce a clear image that is:UprightSame sizeSame shapeVirtual- looks like it is at the same distance behind the mirror as the actual object is in front of the mirror.