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WARM UPWARM UP
ON YOUR INDEX CARD, WRITE ONE SENTENCE ABOUT THE RELATIONSHIP BETWEEN ELECTRICITY AND MAGNETISM!
Light and SoundLight and Sound
In this SECTION:
1) What is light?2) Electromagnetic Spectrum3) Interactions of Light4) Color
What is light?What is light?
Light is an electromagnetic wave!
An electromagnetic wave is a wave that travels through empty space or matter and consists of changing electric and magnetic fields!
How are EM Waves How are EM Waves ProducedProduced
An EM wave can be produced by the vibration of an electrically charged particle. When the particle vibrates, the electric field around it also vibrates. When the electric field vibrates, it creates a vibrating magnetic field. The vibration of both fields together produces an EM wave. The transfer of energy as electromagnetic waves is called RADIATION!
Properties of LightProperties of Light
Light travels in straight lines:
Laser
Light travels VERY FAST – around 300,000 km/sec. This is 880,000
times faster than sound.
At this speed it can go around the world 8 times in one second.
Light travels fastest through empty space!
Light travels much faster than sound. For example:
1) 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.
Shadows
Shadows are places where light is “blocked”:
Rays of light
Properties of Light Properties of Light summarysummary
1) Light travels in straight lines2) Light travels much faster than sound3) Shadows are formed when light is
blocked by an object
2. The Electromagnetic 2. The Electromagnetic SpectrumSpectrum
Entire range of EM waves!
Divided into regions according to wavelength
Where is the highest energy?
EM SPECTRUMEM SPECTRUM
Description
1. Used by police officers to detect the speed of cars by radar2. Energy from the sun that cancause sunburn3. Used in a device that takes images of bones4. Carry television signals to yourhome5. Can produce rainbows when there are water droplets in the sky6. Used to treat forms of cancer or sterilize food
Region of EM spectrum
1. MICROWAVES/RADAR
2. ULTRAVIOLET
3. X-RAYS
4. RADIO
5. VISIBLE LIGHT
6. GAMMA RAYS
VISIBLE LIGHT:NARROW RANGE VISIBLE LIGHT:NARROW RANGE OF WAVELENGTHSOF WAVELENGTHS
LONGEST TO SHORTEST
WAVELENGTH
RedOrangeYellowGreenBlue
IndigoViolet
3. INTERACTIONS OF LIGHT3. INTERACTIONS OF LIGHT
REFLECTION/LAW OF RELFECTIONTYPES OF REFLECTION
LIGHT SOURCE V. REFLECTED LIGHTABSORPTIONSCATTERINGREFRACTIONDIFFRACTION
We see things because they reflect light into our eyes:
Homework
ReflectionReflectionReflection from a mirror:
Incident ray
Normal
Reflected ray
Angle of incidence
Angle of reflection
Mirror
The Law of ReflectionThe Law of Reflection
Angle of incidence = Angle of Angle of incidence = Angle of reflectionreflection
In other words, light gets reflected from a surface at ____ _____ angle it hits it.
The same !
!!
Clear vs. Diffuse ReflectionClear 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
Luminous and non-luminous objects
A luminous object is one that produces light.
An illuminated object is one that reflects light.
Luminous objects Illuminated
FIREFLY
SUN
LIGHT BULB
A VISIBLE OBJECT THAT IS NOT A LIGHT SOURCE
ABSORPTIONABSORPTION
THE ABSORPTION OF LIGHT ENERGY BY MATTER-CAUSES LIGHT TO BECOME
DIMMER. THE FARTHER LIGHT TRAVELS FROM THE SOURCE, THE DIMMER IT
BECOMES
SCATTERING SCATTERING
INTERACTION THAT CAUSES LIGHT TO CHANGE DIRECTION
ALLOWS YOU TO SEE OBJECTS OUTSIDE THE BEAM, BUT BECAUSE LIGHT IS SCATTERED, BEAM BECOMES DIMMER.
RefractionRefraction
Refraction is when waves ____ __ or slow down due to travelling in a different _________. 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, bend. medium
REFRACTION AND COLOR REFRACTION AND COLOR SEPARATIONSEPARATION
RedOrangeYellowGreenBlue
IndigoViolet
Violet light, which has a shorter wavelength, is refracted more than red light
DIFFRACTIONDIFFRACTION
LIGHT CANNOT BEND VERY MUCH BY DIFFRACTION UNLESS IT PASSES THROUGH A VERY NARROW OPENING OR AROUND A SMALL BARRIER.
LIGHT CANNOT DIFFRACT VERY MUCH AROUND LARGE OBJECTS
TRANSMISSIONTRANSMISSION
LIGHT PASSES THROUGH MATTTER.
ALL OF THE LIGHT THAT REACHES YOUR EYES IS TRANSMITTED
THROUGH AIR.
3. Colour3. Colour
White light is not a single colour; it is made up of a mixture of the seven colours 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.
TYPES OF MATTERTYPES OF MATTER
1. TRANSPARENT-LIGHT IS TRANSMITTED THROUGH EASILY
2. TRANSLUCENT-TRANSMITS AND SCATTERS
3. OPAQUE- DOES NOT TRANSMIT LIGHT
How is color determined?How is color determined?The colour an opaque object appears depends on
the colours of light it reflects.
For example, the book only reflects red light so we see it as red!
White
light
Only red light is
reflected
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 light
White
light
Using coloured lightUsing coloured light
If we look at a coloured object in coloured light we see something different. For example, consider a football kit:
White
light
Shorts look blue
Shirt looks red
In different colours of light this kit would look different:
Red
lightShirt looks red
Shorts look black
Blue
light
Shirt looks black
Shorts look blue
The white hair reflects all the light….the black hair absorbs all the light
Colors of Transparent and Colors of Transparent and Translucent ObjectsTranslucent Objects
The color of transparent and translucent objects is determined differently.
Color is determined by what is transmitted.
Glass is clear because it transmits all light. Ginger ale 2-Liters are green because the plastic transmits green light
Mixing coloursMixing 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. Combining colors of light is called color addition
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan
(light blue)
Adding all three makes white again
Adding red and green makes yellow
TV SETSTV SETS
USE RED, BLUE AND GREEN PLATES TO
MAKE ALL THE COLOR YOU SEE!
PIGMENTSPIGMENTS
A PIGMENT is a material that gives a substance its color by absorbing some colors of light and reflecting others.
Chlorophyll is a pigment as is melanin (skin pigment) and paint colors
MIXING PIGMENTSMIXING PIGMENTS
WHEN YOU MIX PIGMENTS TOGETHER, MORE COLORS OF LIGHT ARE ABSORBED OR TAKEN AWAY.
MIXING PIGMENTS IS CALLED COLOR SUBTRACTION
Sound – The basicsSound – The basics
We 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
Drawing sounds…Drawing sounds…
This sound wave has a _____ frequency:
This sound wave has a ___ _frequency:
Drawing sounds…Drawing sounds…
This sound wave has a _____ amplitude (loud):
This sound wave has a _____ amplitude (quiet):
Hearing problemsHearing problems
Our hearing range can be damaged by several things:
1) Too much ear wax!
2) Damage to the auditory nerve
3) Illness or infections
4) Old age (not like Mr Richards)
Other sound effects…Other sound effects…
Like light, sound can be…
1) Reflected – sound reflections are called ______.
2) Refracted – this is why you might sound strange if you try talking underwater
The EarThe Ear
Label your diagram with the following:
These bones are vibrated by the eardrum
This tube carries the sound towards the eardrum
This part is used to help us keep our balance
This part “picks up” the vibrations
This part of the ear contains many small hairs with turn vibrations into an electrical signal
This part connects the ear to the mouth
This part “channels” the sound towards the ear drum
The EarThe Ear