Transcript What is light? - CMSTURTELYTAG

WARM UP
ON YOUR INDEX CARD, WRITE ONE
SENTENCE ABOUT THE RELATIONSHIP
BETWEEN ELECTRICITY AND
MAGNETISM!
Light and Sound
In this SECTION:
1)
2)
3)
4)
What is light?
Electromagnetic Spectrum
Interactions of Light
Color
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 Produced
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 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 summary
1) Light travels in straight lines
2) Light travels much faster than sound
3) Shadows are formed when light is blocked
by an object
2. The Electromagnetic
Spectrum
Entire range of EM
waves!
Divided into regions
according to wavelength
Where is the highest
energy?
EM SPECTRUM
Description
Region of EM spectrum
1. Used by police officers to detect
the speed of cars by radar
2. Energy from the sun that can
cause sunburn
3. Used in a device that takes
images of bones
4. Carry television signals to your
home
5. Can produce rainbows when
there are water droplets in the sky
6. Used to treat forms of cancer
or sterilize food
1.MICROWAVES/RADAR
2.ULTRAVIOLET
3. X-RAYS
4.RADIO
5.VISIBLE LIGHT
6. GAMMA RAYS
VISIBLE LIGHT:NARROW RANGE
OF WAVELENGTHS
LONGEST TO SHORTEST
WAVELENGTH
Red
Orange
Yellow
Green
Blue
Indigo
Violet
3. INTERACTIONS OF LIGHT
REFLECTION/LAW OF RELFECTION
TYPES OF REFLECTION
LIGHT SOURCE V. REFLECTED LIGHT
ABSORPTION
SCATTERING
REFRACTION
DIFFRACTION
We see things because they
reflect light into our eyes:
Homework
Reflection
Reflection from a mirror:
Normal
Reflected ray
Incident ray
Angle of
incidence
Angle of
reflection
Mirror
The Law of Reflection
Angle of incidence = Angle of reflection
In other words, light gets reflected from a surface at
____ _____ angle it hits it.
The
same !!!
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
Luminous and non-luminous objects
A luminous object is one that produces light.
An illuminated object is one that reflects light.
Luminous objects
FIREFLY
SUN
LIGHT BULB
Illuminated
A VISIBLE
OBJECT THAT
IS NOT A
LIGHT SOURCE
ABSORPTION
THE ABSORPTION OF LIGHT ENERGY BY
MATTER-CAUSES LIGHT TO BECOME
DIMMER. THE FARTHER LIGHT TRAVELS
FROM THE SOURCE, THE DIMMER IT
BECOMES
SCATTERING
INTERACTION THAT
CAUSES LIGHT TO
CHANGE DIRECTION
ALLOWS YOU TO SEE
OBJECTS OUTSIDE
THE BEAM, BUT
BECAUSE LIGHT IS
SCATTERED, BEAM
BECOMES DIMMER.
Refraction
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
SEPARATION
Violet light, which has a shorter wavelength, is
refracted more than red light
Red
Orange
Yellow
Green
Blue
Indigo
Violet
DIFFRACTION
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
TRANSMISSION
LIGHT PASSES
THROUGH MATTTER.
ALL OF THE LIGHT
THAT REACHES YOUR
EYES IS
TRANSMITTED
THROUGH AIR.
3. 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 MATTER
1.
TRANSPARENT-LIGHT
IS TRANSMITTED
THROUGH EASILY
2. TRANSLUCENTTRANSMITS AND
SCATTERS
3. OPAQUE- DOES NOT
TRANSMIT LIGHT
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 pair of purple trousers would reflect purple light
(and red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colours:
White
light
Using coloured light
If we look at a coloured object in coloured
light we see something different. For
example, consider a football kit:
Shirt looks red
White
light
Shorts look blue
In different colours of light this kit would look different:
Red
light
Shirt looks red
Shorts look black
Shirt looks black
Blue
light
Shorts look blue
The white hair reflects
all the light….the black
hair absorbs all the light
Colors of Transparent and
Translucent 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 colours
White 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 red
and green
makes yellow
Adding blue and
green makes cyan
(light blue)
Adding all
three makes
white again
TV SETS
USE RED, BLUE AND
GREEN PLATES TO
MAKE ALL THE COLOR
YOU SEE!
PIGMENTS
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 PIGMENTS
WHEN YOU MIX PIGMENTS TOGETHER,
MORE COLORS OF LIGHT ARE
ABSORBED OR TAKEN AWAY.
MIXING PIGMENTS IS CALLED COLOR
SUBTRACTION
Sound – 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…
This sound wave has a
_____ frequency:
This sound wave has a
___ _frequency:
Drawing sounds…
This sound wave has a
_____ amplitude
(loud):
This sound wave has a
_____ amplitude
(quiet):
Hearing 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…
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 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 Ear