REFLECTION AND REFRACTION HUAIZI TONG BINGYANG LIU.

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