3 This energy travels to Earth in a vacuum of space. The Sun gives off huge amounts of energy called electromagnetic radiation or radiant energy.This energy travels to Earth in a vacuum of space.
4 Some of this E-M orradiant energyyou can seesome you can’tVisible light you can see!Hence the word visible!Most types of E-M or radiant energy are invisible.For example:Infrared radiationUltraviolet radiation (ouch!)X-raysMicrowavesRadio wavesGamma rays
6 Light starts many chemical reactions such as photosynthesisRadiant energycan cause changes in matter The light energy is changedto other forms of energyFor example:Sunlight heats thewater in the oceanWhat aboutsolar power?Is this a change in the form of energy?
7 Remember chemical reactions? Many give off light.
8 So, how does light travel? Photons! Tiny invisible particles of energy!Photons are energy, not matter, so no weight!
9 Wow, I am as light as a photon! But, I still don’t get it!How do the photons get to where they are going?
11 Light Waves like this! A wave is energy that moves through a Geez! Do I always have to tell you guys everything?A wave is energy that moves through amedium (solid, liquid, or gas)
12 But however they travel….. light waves all travel through space at the same speed and they can all travel through a vacuum.Nothing is a fast as the speed of light….well almost nothing!It travels 300,000 km/s!That’s fast!Light could travel around the world 7.5 times in 1 second!
13 Waves – light waves that is Crest – highest point of the waveTrough – lowest part of the waveHmmm.. Does this sound familiar?Who remembers waves from our ocean unit?
14 Frequency Wavelength Amplitude Light Waves are measured according to:Frequencythe number of waves that pass a point in a specific amount of time (like a second)Wavelengthmeasurement from the crest of one wave to another crestAmplitudemeasurement from crest to the midline, or crest to troughdivided by two
15 High frequency wave= short wave length = more energyLow frequency waves =longer wave length =less energy
18 Light behaves in different ways when it strikes different things
19 Light slows down - bends – or bounces back when it travels through different mediums like gas, liquids, or solidsWe’ll learn in the next unit that sound is just the opposite!Sound waves speed up when they travel throughdifferent mediums such as gas, liquids, or solids.
20 Visible Light What we see is white light that is actually made up of many colors of lightWe can only seethese colors whenthey arereflected or refracted
21 ROYGBIV – the visible light spectrum RedOrangeYellowGreenBlueIndigoViolet
22 ROYGBIV The visible light spectrum Red – Orange – Yellow – Green – Blue – Indigo - Violet
23 Reflection the return of light or sound as it bounces off a surface Reflection is the way we see most things!
24 The colors of light that an object reflects are the colors we see. For example: an apple absorbs most of the sunlight that strikes it.The rest of the light – the red part – reflects off the apple.That’s why the apple appears red to us.Cool heh?
25 Refractionthe bending&slowing down oflight waves
26 refraction A prism works like a rainbow! It separates white light into the spectrum known asROY G BIV. When light passes into the prism glass it slows down and bends. This is known asrefraction
27 Rainbows are produced when white light strikes drops of water. Each drop acts like a prism that separates the white light intoROYGBIV.
28 Opaque No light passes through Example – wood, foil, 50 sheets of paper
29 Allows all light rays to pass through Example - glass, shallow water TransparentAllows all light rays to pass throughExample - glass, shallow water
30 Allows some light rays to pass through TranslucentAllows some light rays to pass throughExample: wax paper – one piece of paper
31 Light ActivityEach table will have one container of objects.Experiment with the prism to find ROYGBIVExperiment with the disk to find ROYGBIVAnswer questions on the ROYGBIV worksheetFind your What’s Blocking the Light worksheets in packetChoose an object such as a pencil or eraser.Now take a material that you believe is transparent fromYour box of goodies.Observe what happens when you place it over the object youhave chosen.Draw in the cloud what you observe.Write about what you observeDo the same for translucent and opaqueWhen finished, try experimenting with other materials in boxFill in boxes with materials that are transparent, translucent and opaqueFinish worksheet.
32 Refractionthe bending & slowing down of light waves when they pass from one kind of matter to another
33 A mirage is an example of light refraction. The difference in air temperature bends the light
34 Concave Lens A lens that is wider at the edges than in the middle, and That refracts light rays so they bend outward
35 Convex Lens A lens that is wider in the middle than it is at the edges It refracts light rays so they come together.
36 Nearsighted means you can see close up, but not far away. Concave lenses correct nearsighted vision.Farsighted means you can see faraway objects,but not close up objects.Convex lenses correct farsighted visionOther examples of convex lenses are:magnifying glasses, telescopes, microscopes, & binoculars
37 How do we see? Our eyes are like cameras The pupil is the opening Iris – controls the amount of light that enters the eyeRetina – a layer of light sensitive cells at the back of the eyeThe retina sends a signal to our brain to tell us what we are seeing