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REFLECTION AND REFRACTION

REFLECTION AND REFRACTION. HUAIZI TONG BINGYANG LIU. What is Reflection?.

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REFLECTION AND REFRACTION

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  1. REFLECTION AND REFRACTION HUAIZI TONG BINGYANG LIU

  2. What is Reflection? • 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.

  3. Reflection of light • 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.

  4. Reflection of light in physics • 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.

  5. Law of Reflection • 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.

  6. More practical applications • 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

  7. What is Refraction? • Refraction is the bending of a wave when it enters a medium where it's speed is different. Light wave Sound wave etc… Water wave

  8. 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.

  9. Refraction of Light by Water 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.

  10. The amount of bending depends on the indices of refraction of the two media and is described quantitatively bySnell's Law

  11. 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.

  12. 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.

  13. 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.

  14. 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/CommunityC ollege/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

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