Presentation on theme: "Light and Sound In this unit: Properties of light Reflection Colours"— Presentation transcript:
1 Light and Sound In this unit: Properties of light Reflection Colours RefractionProperties of soundHearing
2 Part 1 – Properties of Light Light travels in straight lines:Laser
3 Light travels VERY FAST – around 300,000 kilometers per second. At this speed it can go around the world 8 times in one second.
4 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.
5 We see things because they reflect light into our eyes: Homework
6 Luminous and non-luminous objects A luminous object is one that produces light.A non-luminous object is one that reflects light.Luminous objectsReflectors
7 ShadowsShadows are places where light is “blocked”:Rays of light
8 Energy in Light-There is a lot of energy in light. -For example, when you stand in the sun you feel the sun’s energy through heat. -If you absorb too much of that energy, you can get a sunburn. -A lamp doesn’t have as much energy as the sun- you can’t get sunburned by a lamp. -However, a lamp does give off heat because of the electric current it takes to make it work.
9 Properties of Light summary Light travels in straight lines.Light travels much faster than sound.We see things because they reflect light into our eyes.Shadows are formed when light is blocked by an object.Light gives off energy in the form of heat.
10 Part 2: Reflection-When light hits an object, the object affects the path of the light. -An object can absorb light, make it bounce off, or let it pass through. -Some light energy is absorbed. Darker objects absorb more light energy-that’s why you are hotter when you wear dark colors on a hot day. -Objects don’t absorb all the light that hits them. Some of the light bounces off. Reflection is the bouncing of light from a surface.
11 Part 2:Reflection-Usually, light scatters in many directions when it is reflected. -A smooth surface reflects light in a clear and predictable pattern. -Have you ever seen a reflection in clear windows on a building? -Looking in a mirror can also get you a smooth reflection, but it gives you a backward image.
12 Reflection from a mirror: NormalIncident 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 RefractionWhen light moves from water to air, its speed changes. The change in speed makes the beam of light bend. This bending of light is called refraction. Refraction is bending light.When a pen is placed in water it looks like this:Refracted light can make a solid object look like it is broken into two parts. It looks like that because the light from the part of the pencil that is under the water reaches your eyes on a different path.
15 Translucent Materials -Materials that let some light through are called translucent. An example of a translucent material is a frosted light bulb.
16 Transparent Materials -A transparent material allows most of the light that hits it to pass through it.-Most glass, water, and some plastics are transparent.-Transparent objects don’t scatter light, but they do refract it.
17 Opaque Materials-Materials that do not allow any light to pass through them are opaque.-Opaque materials absorb all the light into them.-Metal, wood, and most of your body is opaque.
18 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:
19 Light and Color-As light enters a prism, the light waves change directions and separate (this is an example of refraction).-You are able to see all the colors of the rainbow when the colors separate.-You can remember all the colors of the rainbow with ROYGBIV.-When have you seen a rainbow of color?
20 The colors of the rainbow: RedOrangeYellowGreenBlueIndigoViolet
21 Lenses -A lens is a curved, transparent object that refracts light. -There are different types of lenses with different types of curves.
22 Convex Lens -A convex lens is thicker in the middle than at the edges. -As light waves move through the lens, they bend towards the thickest part-the middle.-A convex lens makes light waves come together and make objects appear larger or magnified.
23 Concave Lens-A concave lens is thicker at the edges than in the middle.-As light waves enter the lens, they bend toward the thicker part- the ends.-The concave lens makes light waves spread out and this makes objects appear smaller.
24 Adding coloursWhite light can be split up to make separate colours. These colours can be added together again.The primary colours 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
25 Only red light is reflected Seeing colourThe colour an object appears depends on the colours of light it reflects.For example, a red book only reflects red light:HomeworkWhitelightOnly red light is reflected
26 A white hat would reflect all seven colours: 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 colours:Whitelight
27 Using coloured lightIf we look at a coloured object in coloured light we see something different. For example, consider a football kit:Shirt looks redWhitelightShorts look blue
28 In different colours of light this kit would look different: RedlightShirt looks redShorts look blackShirt looks blackBluelightShorts look blue
29 Some further examples: ObjectColour of lightColour object seems to beRed socksRedBlueBlackGreenBlue teddyGreen camelMagenta bookHomework
30 Using filters Red Filter Filters can be used to “block” out different colours of light:Red FilterMagenta Filter
31 Investigating filters Colour of filterColours that could be “seen”RedGreenBlueCyanMagentaYellow
33 Words – slowly, low, high, quickly Sound – The basicsWe hear things when they vibrate.If something vibrates with a high frequency (vibrates very ______) we say it has a _____ pitch.If something vibrates with a low frequency (vibrates ______) we say it has a ____ pitch.The lowest frequency I could hear was…Words – slowly, low, high, quickly
34 Drawing sounds… This sound wave has a _____ frequency:
35 Drawing sounds… This sound wave has a _____ amplitude (loud): This sound wave has a _____ amplitude (quiet):
36 Hearing problems Our hearing range can be damaged by several things: Too much ear wax!Damage to the auditory nerveIllness or infectionsOld age (not like Mr Richards)
37 Other sound effects… Like light, sound can be… Reflected – sound reflections are called ______.Refracted – this is why you might sound strange if you try talking underwater
38 The Ear Label your diagram with the following: These bones are vibrated by the eardrumThis tube carries the sound towards the eardrumThis part is used to help us keep our balanceThis part “picks up” the vibrationsThis part of the ear contains many small hairs with turn vibrations into an electrical signalThis part connects the ear to the mouthThis part “channels” the sound towards the ear drum