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REFLECTION AND REFRACTION
HUAIZI TONG
BINGYANG LIU
Reflection is the change in direction of a
wavefront at an interface between two different
media so that the wavefront returns into the
medium from which it originated. The reflection of
light, sound and water waves are common
examples of reflection.
What is Reflection?
Reflection of light is either specular or diffuse depending on the nature of
the interface. Furthermore, if the interface is between a dielectric and a
conductor, the phase of the reflected wave is retained, otherwise if the
interface is between two dielectrics, the phase may be retained or
inverted, depending on the indices of refraction.
A mirror is the most common model for specular light reflection. Reflection
also occurs at the surface of transparent media, such as water or glass.
Reflection of light
In the picture, a light ray IO strikes a plane
mirror at point O, and the reflected ray is RO.
By projecting an imaginary line through point
O perpendicular to the mirror- NO, known as
the normal, we can measure the angle of
incidence, i and the angle of reflection, r. The
law of reflection states that i= r, or in other
words, the angle of incidence equals the angle
of reflection.
Reflection of light in physics
If the reflecting surface is very smooth, the reflection of light that
occurs is called specular or regular reflection. The laws of reflection
are as follows:
1. The incident ray, the reflected ray and the normal to the
reflection surface at the point of the incidence lie in the same
plane.
2. The angle which the incident ray makes with the normal is equal
to the angle which the reflected ray makes to the same normal.
Law of Reflection
1. A MOVIE SCREEN
2. INDIRECT ROOM LIGHTING
3. A LASER
4. FACED DIOMAND REFLECTIONS
5. TOTAL INTERNAL REFLECTIONS IN FIBER OPTICS
6. WE CAN SEE MOOM BECAUSE OF THE REFLECTED LIGHT
More practical applications
Refraction is the bending of a wave when it enters a
medium where it's speed is different.
What is
Refraction?
Light wave Sound wave Water wave etc…
For example, if you look straight
down at an object at the bottom of
a glass of water, it looks closer
than it really is. A good way to
visualize how light and sound
refract is to shine a flashlight into
a bowl of slightly cloudy water
noting the refraction angle with
respect to the incident angle.
We can see the "broken pencil"
effect because of the refraction
at the water surface .
Submerged objects always
appear to be shallower than they
are since the light from them
changes angle at the surface,
bending downward toward the
water.
Refraction of Light by Water
The amount of bending depends on the indices of
refraction of the two media and is described
quantitatively by Snell's Law
Snell's Law Snell's Law describes the relationship between the angles
and the velocities of the waves. Snell's law equates the ratio of material velocities V1 and V2 to the ratio of the sine's of incident (Q1) and refracted (Q2) angles, as shown in the following equation.
Where: VL1 is the longitudinal wave velocity in material 1. VL2 is the longitudinal wave velocity in material 2.
Huygens' principle
Dutch physicist Christian Huygens
Each point on the leading surface of a
wave disturbance may be regarded as a
secondary source of spherical waves,
which themselves progress with the
speed of light in the medium and whose
envelope at later times constitutes the
new wavefront.
For example, if two rooms are
connected by an open doorway and a
sound is produced in a remote corner
of one of them, a person in the other
room will hear the sound as if it
originated at the doorway. As far as the
second room is concerned, the
vibrating air in the doorway is the
source of the sound. The same is true
of light passing the edge of an
obstacle, but this is not as easily
observed because of the short
wavelength of visible light.
References In Wikipedia. Retrieved from
http://en.wikipedia.org/wiki/Refraction, http://en.wikipedia.org/wiki/Refraction and http://en.wikipedia.org/wiki/Christiaan_Huygens
In NDT Resource Center. Retrieved from http://www.ndted.org/EducationResources/CommunityCollege/Ultrasonics/Physics/refractionsnells.htm
In HYPERPHYSICS. Retrieved from: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html and
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polref.html