Presentation on theme: "Light Energy & How light interacts with matter"— Presentation transcript:
1 Light Energy & How light interacts with matter Let there be light!!!Light Energy &How light interacts with matter
2 What is light?Light is a form of radiant energy that you can detect with your eyes. Light energy comes from chemical energy, electrical energy and nuclear energy.Light can pass through anything that is transparent, sort of passes through translucent objects (frosted window) but doesn't make it through opaque objects such as a brick wall.
3 Light travels in straight lines: Properties of LightLight travels in straight lines:Laser
4 Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.
5 Light travels much faster than sound. For example: Thunder and lightning start at the same time, but we will see the lightning first.
6 We see things because they reflect light into our eyes: Homework
7 Luminous and non-luminous objects A luminous object is one that produces light.A non-luminous object is one that reflects light.Luminous objectsReflectorsSunLight bulbsFireWaterMirrorsSmooth shiny surfaces
8 ShadowsShadows are places where light is “blocked”:Rays of light
9 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
10 Reflection Reflection from a mirror: Mirror Normal Angle of incidence Incident rayReflected rayAngle of incidenceAngle of reflectionMirror
11 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 !!!
12 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
13 Using mirrorsTwo examples:2) A car headlight1) A periscope
14 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.
15 A rainbow would form a complete circle, not just an arc, if the ground didn't get in the way Rainbows always face the observer. As the observer moves, the rainbow moves.And sorry, no one can ever get to the "pot of gold" at the end of the rainbow
16 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
17 A white hat would reflect all seven colors: A pair of purple shorts 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
19 Words – speed up, direction, 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 ruler is placed in water it looks like this:In this case the light rays are slowed down by the water and are _____, causing the ruler to look odd. The two mediums in this example are ______ and _______.Words – speed up, direction, water, air, bent
20 Key Vocabulary Reflection – The light energy that bounces off objects. Refraction – The bending of light rays when they pass through a substance.
21 Convex and Concave Mirrors Images in convex mirrors Images in concave mirrors are always smaller are always bigger.
22 Convex and Concave Lenses Convex Lenses are used as a MagnifierConcave Lenses are used as a De-magnifier
23 Convex LensesPeople who are farsighted have trouble seeing things that are close to them (reading) Glasses or contacts with convex lenses magnify the printMovie projectors use convex lenses. As light from the bulb shines through the film, light rays spread apart. As these rays pass through the projector lens, they bend toward each other again.
24 Concave LensesConcave lenses help people who are nearsighted. These people have trouble seeing distant objects. Concave lenses bend light rays outward just enough to make distant objects seem closer.Some cameras have a concave lens in their viewfinder, you see a small version of what the final photograph wil look like.
25 Key Vocabularylens – a piece of clear material that bends, or refracts, light rays passing through it.Convex lens – is thicker in the middle than at the edges.Concave lens – is thicker at the edges than in the middle.
26 Using Light, Lenses, and Mirrors for space exploration
27 Refracting TelescopeIn Galileo's version, light entering the far end (1) passed through a convex lens (2), which bent the light rays until they came into focus at the focal point (f). The eyepiece (3) then spread out (magnified) the light so that it covered a large portion the viewer's retina and thus made the image appear larger.
28 Reflecting TelescopeIn Newton's version, light streaming in one end (1) reflected off a concave mirror fixed inside the other end (2), then off a flat mirror set an angle (3). The light came into focus at the focal point (f) and then was magnified for the viewer by the eyepiece (4).