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Transcript
REFRACTION AND REFLECTION
POLARIZATION OF LIGHT
Emily Kozlowski and April Mante
DEFINITION OF REFRACTION
• Refraction is the change in direction of a wave due to a
change in its speed. This is most commonly observed
when a wave passes from one medium to another at an
angle.
http://www.stmary.ws/highschool/physics
/home/notes/waves/refraction/fishRefract
ion.html
Is It really bending????????
• Straight or bent? What happens when you look
at the pencil through the side of the glass? Light
play tricks on your eyes. The pencil looks
bent. This is because light travels slower
through water than through air. As the light
enters the glass of water it slows down(changes
direction) and as it leaves the glass it speeds up
again – therefore making the pencil look as
though it is bent
Refraction
• A lens is a piece of transparent
material. It is usually made of glass
and has at least one curved surface.
• The curved surface/surfaces of a lens
bends the light.
The angle of incidence is measured from the normal to
the incident ray.
The angle of refraction is measured from the normal to
the refracted ray.
• If light enters a more optically dense material,
the speed decreases and the light bends
towards the normal.
• If light enters a less optically dense material, the
speed increases and the light bends away from
the normal.
•The angle of incidence that results in an angle of refraction
of 90 degrees is call the critical angle.
•If the angle of incidence is greater than the critical angle
total internal reflection occurs.
Did you know....
A sunset is an optical illusion
Refraction allows you
to see the sun
even after it has set.
Reflection
•Reflection is the change in direction of a wave
front at an interface between two different
media so that the wave front returns into the
medium from which it originated from.
•A flat mirror called a plane mirror is a good
reflector of light. A normal is formed when a
ray of light strikes the mirror at a right angle.
Reflection
•Reflection- the return of light, heat, sound, etc.,
after striking a surface.
•bouncing of light off a mirror or mirror-like
surface.
• -Reflection may even occur on water and clouds
• Mainly, there are two types of reflection, specular and
diffused.
• Light being reflected of a smooth surface is Specular.
When light strikes this smooth surface, all the reflected
rays are in line with each other. An image is formed.
• If the surface is rough, the light scatters
b. Diffuse Reflection – reflection off
an irregular surface causing light to
scatter (no image)
Regular Reflection –
reflection off a polished
surface (produces images)
Polarization of Light
• Polarizing filters are used in photography and in
certain kinds of sunglasses.
• But polarization is also used in digital watches
and laptop screens.
QUIZ:
1. ________ is the change in direction of a wave due to a change in
its speed
2. The ___________ is measured from the normal to the refracted
ray.
3._____________- reflection off an irregular surface causing
light to scatter
4._________– reflection off a polished surface
5. If light enters a less optically dense material, the speed ______
and the light bends ____ from the normal
6. The angle of incidence that results in an angle of refraction of
90 degrees is call the__________.
ANSWERS
1.Refraction
2.Angle of refraction
3.Diffuse reflection
4.Regular reflection
5.Increases , away
6.Critical angle
http://www.stmary.ws/highschool/physics/home/animations3
/default.htm
http://www.physicsclassroom.com/Class/
http://www.flickr.com/photos/isabelfotografie/page7/
http://www.bing.com/images/search?q=angle+of+incidence&F
ORM=BIFD#focal=698642f006cbe01c3d956f4712d07689&furl
=http%3A%2F%2Fsciencecity.oupchina.com.hk%2Fnpaw%2Fst
udent%2Fglossary%2Fimg%2Fangle_of_incidence.jpg
http://en.wikipedia.org/wiki/Reflection
Refraction
/reflection/polarization of light
By Nick Valentin And Keaon
Naghizadeh
What is light?
• Light is an electromagnetic radiation that can
produce a visual sensation, which is used in
many ways like refraction, reflection and
polarization of it.
What is Refraction ?
• Occurs when light passes into a new material
and starts to move at a different speed. If the
ray hits the surface of the material at an angle,
the ray will be bent.
• Example is when you stick a pencil into a glass of
water the rays form the light in the room hits the
surface of the pencil at a different angle and
different speed which cause the pencil to look
distorted .
Examples of Refractions
Snell’s law of refraction
• The bending of light called refraction was first
studied by Rene Descartes and Willebrord Snell,
around the time of Kepler and Galileo.
• To understand their result you have to define to
angles, The angle of incidence is the angle at
which the light ray strikes the surface . It is
measure from the normal to the surface. The
second angle, is the angle of refraction . This is
the angle in which the transmitted light leaves
the surface.
Continue Snell’s Law
• In 1621 Snell found that when light went from air into a
transparent substance , the sines of the angles were
related by the equation .
• N1Sinθ1=n 2 Sinθ1 .
• In this equation “N” is a constant that depends on the
substance , not on the angles called the index of
refraction.
• θ1 is the angle at which the light rays strikes the surface ,
which is measure from the normal to the surface
• θ2 is the angle at which the transmitted light that leaves
the surface.
Reflection
• Reflected waves are simply those waves
that are neither transmitted or absorbed,
but are reflected from the surface of the
medium they encounter.
• Reflection does not just happen with a
mirror, it happens with any flat surface
that doesn’t transmitted or absorbed.
Law of Reflection
• It states that when an object bounces off a flat
surface, the angle it at which it hits the surface
will be equal to the angle at which it bounces
away.
• law of reflection can also be stated as that the
angle of incidence is equal to the angle of
reflection
• No matter what the incidence and refection
angle must be equal.
Examples of the law of reflection
• IF you hit a pool ball against a bumper of a pool
table, the initial angle use to hit the ball against
the wall is the incidence angle.
• As the ball hits the bumper it rebounds at an
angle that is equal to the incidence .This new
angle is called reflection.
Polarization of
light
• The process of transforming unpolarized light
into polarized light is known as Polarization.
• There are to specific types of polarization called
polarization by filtration and polarization by
reflection
• To full understand the concept of this look at
this figure
Polarization of Filtration
• Polarization can be understood by considering a
rope model of light waves. The transverse
mechanical waves in the rope represent
transverse light waves. The slots represent what
is referred to as the polarizing axis of the
polarizing medium.
Quiz!!!!!
• 1. Angle of incidence=
a)optical density
b)angle of reflection
c)index of refraction
• 2. One of the laws of reflection of light states :
The angle of _______ is always equal to the angle
of reflection.
•
a)convergence
b) incidence
c) refraction
More quiz
3.What is "refraction"?
a)When light goes into space
b)When light bounces off another object
c)When light bends at a boundary
d)When light passes through water and continues
in straight line
Even more
4.What does "Snell's Law" state?
a)A ray of light bends in such a way that the ratio
of the sine of the angle of incidence to the since
of the angle of refraction is a constant
b)That light does not come from the sun
c)That light does come from the sun
d)That everyone is unique
Believe it or not…moree
5.What is the ray, which first strikes a surface,
called?
a)Primary ray
b)Primary color
c)Reflection ray
d)Incident ray
Answer Key
•
•
•
•
•
1.B
2.B
3.C
4.A
5.D
Bibliography
• hyperphysics.phyastr.gsu.edu/Hbase/geoopt/r
efr.html
• http://id.mind.net/~zona/mstm/physics/light/r
ayOptics/reflection/reflection1.html
• http://www.worsleyschool.net/science/files/refl
ectionlaw/page.html
• http://en.wikipedia.org/wiki/Snell's_law
• Physics Principles and Problem Text book