3 Radiant Light Wavelengths Visible Light: We only see this wavelength!
4 Visible LightProperties of lightReflectionColorsRefraction
5 Part 1 – Properties of Light Light travels in straight lines:Laser
6 Light travels VERY FAST – around 300,000 kilometers per second. At this speed it can go around the world 8 times in one second.
7 Light travels much faster than sound. For example: Thunder and lightning start at the same time, but we will see the lightning first.2) When a starting pistol is fired we see the smoke first and then hear the bang.
8 We see things because they reflect light into our eyes: Science Homework
9 Luminous and non-luminous objects A luminous object is one that produces light.A non-luminous object is one that reflects light.Luminous objectsReflectors
10 ShadowsShadows are places where light is “blocked”:Rays of light
11 Properties of Light summary Light travels in straight linesLight travels much faster than soundWe see things because they reflect light into our eyesShadows are formed when light is blocked by an object
12 Part 2 - Reflection Reflection from a mirror: Mirror Normal Incident rayReflected rayAngle of incidenceAngle of reflectionMirror
13 Angle of incidence = Angle of reflection The Law of ReflectionAngle of incidence = Angle of reflectionIn other words, light gets reflected from a surface at ____ _____ angle it hits it.The same !!!
14 Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection:Rough, dull surfaces have a diffuse reflection.Diffuse reflection is when light is scattered in different directions
15 What Happens When Light Strikes Objects? Transparent- light passes throughTranslucent- some scattered light passes through and casts a light shadowOpaque-blocks all light and casts a dark shadow
16 Using mirrorsTwo examples:2) A car headlight1) A periscope
17 ColorWhite light is not a single color; it is made up of a mixture of the seven colors of the rainbow.We can demonstrate this by splitting white light with a prism:This is how rainbows are formed: sunlight is “split up” by raindrops.
18 The colors of the rainbow: RedOrangeYellowGreenBlueIndigoViolet
19 Adding colorsWhite light can be split up to make separate colors. These colors can be added together again.The primary colors of light are red, blue and green:Adding blue and red makes magenta (purple)Adding blue and green makes cyan (light blue)Adding red and green makes yellowAdding all three makes white again
20 Only red light is reflected Seeing colorThe color an object appears depends on the colors of light it reflects.For example, a red book only reflects red light:HomeworkWhitelightOnly red light is reflected
21 A white hat would reflect all seven colors: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):Purple lightA white hat would reflect all seven colors:Whitelight
22 Using colored lightIf we look at a colored object in colored light we see something different. For example, consider a this outfit:Shirt looks redWhitelightShorts look blue
23 In different colors of light this outfit would look different: RedlightShirt looks redShorts look blackShirt looks blackBluelightShorts look blue
24 Some further examples: ObjectColor of lightColor object seems to beRed socksRedBlueBlackGreenBlue teddyGreen camelMagenta bookHomework
25 Using filters Red Filter Filters can be used to “block” out different colors of light:Red FilterMagenta Filter
26 Investigating filters Color of filterColors that could be “seen”RedGreenBlueCyanMagentaYellow
28 Words – speed up, water, air, bent RefractionRefraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this:In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______.Words – speed up, water, air, bent
29 Lenses Refract Light Convex Lens Thicker in the center Bends light waves togetherMagnifies objectYour eye has a double convex lensUsed in telescopes and binocularsConcave LensThicker on the edgesBends light waves apartObjects appear smallerMakes details clearerUsed in projectorsEyeglasses and contacts use both types of lenses