Reflection of light (Physics)

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  1. 1. PHYSICS Propagation & Reflection Of Light
  2. 2. Light Light was considered as mysterious thing in olden days. Light deals with luminous energy, energy which causes the sensation of vision. Light is brightness that comes from an object producing light , called luminous body (sun). Light comes from atoms. Atoms that produce light have either gained energy by absorbing light from an other source or by being struck by other particles. It is this extra energy that causes an atom to give off light. Study of light and interaction of light and matter is known as optics.
  3. 3. Properties of Light Rectilinear propagation. Shadow formation Reflection. Refraction. Diffraction. Dispersion. Polarization. Interference.
  4. 4. Properties of Light Shadow Formation= The straight rays of light passing the edges of non transparent( opaque) body, leave a sharp shadow of that body in the way of light.
  5. 5. Properties of Light Rectilinear Propagation= Light travels in straight lines very fast. Laser
  6. 6. Properties of Light Reflection = when light strikes smooth shining surface it returns back into same medium. Incident ray Reflected ray Normal
  7. 7. Properties of Light Refraction = When light enters from one transparent medium into another , it changes its path.
  8. 8. air glass normal angle of refraction angle of incidence Properties of Light
  9. 9. Properties of Light Diffraction = It is apparent bending of light waves around the obstacle in its path.
  10. 10. Dispersion = It refers to the break down of white light( sun light) into its constituent colours. Properties of Light
  11. 11. Properties of Light Interference = It is the phenomenon that occurs when two beams of light meet, to give brighter beam (constructive interference) or to produce less bright beam( destructive interference).
  12. 12. Properties of Light Polarization= It is the direction, the wave is vibrating in.
  13. 13. Plane-polarized waves Plane-polarized waves Circularly polarized waves
  14. 14. The reflection of Mount Hood in Mirror Lake.
  15. 15. Double reflection: The sun is reflected in the water, which is reflected in the paddle.
  16. 16. Reflection Of Light When light traveling through one medium strikes the surface of another medium(Mirror), part of it is returned back in the first medium in a particular direction, such phenomenon is called Reflection of Light
  17. 17. Regular Reflection Or Specular Reflection When rays of light strike the smooth shining surface ( plane mirror) they are reflected in the same direction , it is called regular reflection. In it at different places of surface, the values of incident angle ( Li) are same.
  18. 18. Irregular Reflection Or Diffused Reflection When rays of light strike rough surface(Earth), they are reflected in different directions, it is called irregular reflection. In it at different places of surface the value of incident angle(Li) are not same.
  19. 19. Laws Of Reflection Of Light The incident ray, the reflected ray and the normal all lie in the same plane. The angle of incident(li) is equal to the angle of reflection (Lr).
  20. 20. Position & Nature Of Image Formed By Plane Mirror In plane mirror image formed is of the same size as the object. Image is as far behind the mirror as the object in front of the mirror. Image is virtual and laterally inverted.
  21. 21. Applications Of Plane Mirror It is used as a looking glass. In the field of medicine, it is used by Dentists and Ophthalmic surgeons. It is used in electric meters, in special head lights, light microscopes, periscope and kaleidoscope.
  22. 22. Applications Of Plane Mirror As looking glass Periscope
  23. 23. Kaleidoscope Microscope
  24. 24. Applications Of Plane Mirror Ophthalmoscope Electric Meter
  25. 25. Applications Of Plane Mirror Plane Mirror Head Light
  26. 26. Pin Hole Camera A pin hole camera is a simple camera without a lens and with aperture , effectively alight - proof box with a small hole in one side. Light rays from an object pas through a small hole to form an inverted image , on semitransparent paper at the back of the box. It is also known as camera obscura ( dark room).
  27. 27. Pin Hole Camera Hole Image Semitransparent paper Object
  28. 28. Types Of Mirror Plane Mirror Curved Mirror Parabolic Mirror
  29. 29. Spherical Mirror A mirror having curve surface is termed as spherical mirror, being a part of large hollow mirror) or curved mirror.
  30. 30. Types Of Spherical Mirrors Spherical mirrors are classified into following two types, according to how they reflect light rays from a distant source.
  31. 31. Terms Used In Spherical mirror CP = Radius of curvature. C = Centre of curvature. PO = Principal axis. P = Pole of mirror. F = Focus of mirror. PF(f) = focal length of mirror. XY = Aperture of mirror.
  32. 32. Concave Mirror Its reflecting surface caves inwards. It is converging mirror. It forms real image. Its focal length is taken positive ( +ve ).
  33. 33. Convex Mirror Its reflecting surface bulges outwards. It is diverging mirror. It forms virtual image. Its focal length is taken negative (-ve ).
  34. 34. Uses Of Spherical Mirrors Concave Mirrors=(1)These are used in search light, head light and flash light.(2)These are used as objective in Reflecting Telescopes. (3) These are used as magnifiers.(4) These are used in solar heaters.
  35. 35. Reflecting Telescope Uses Of Concave Mirror
  36. 36. Uses Of Concave Mirror Head Lights As Magnifier
  37. 37. Uses Of Spherical Mirrors Convex Mirror = These having vast field vision are used as side mirrors in motor vehicles.
  38. 38. Uses Of Spherical Mirrors
  39. 39. Rules For Light Rays In concave Mirror A. The ray of light C,this is reflected back through C. B. The ray of light parallel to the principal axis, is reflected through F. C. The ray of light through F, is reflected parallel to the principal axis.
  40. 40. Ray diagrams
  41. 41. Description Of An Image To describe an image, fallowing four aspects need to be determined. Its location = Where it is in relation to the mirror. Its size =How big it is compared with the object. Its orientation = Where it is upright or upside down. Its nature = Where or not the image can be captured on a screen.
  42. 42. Images Formed By concave Mirror I. If object is placed beyond C.Its image will be formed near F ( out side the focus of mirror) the focus of mirror. Image will be real, inverted and smaller than the object.
  43. 43. II. If object is placed at C .Its image will be formed at C.image will be real, inverted and of same size as object. Images Formed By concave Mirror
  44. 44. Images Formed By concave Mirror III.If object is placed b/w C and F. its image will be formed out side the C. Image will be real, inverted and larger than object.
  45. 45. Images Formed By concave Mirror IV. If object is placed inside the focus(F). Its image will be formed behind the mirror.Image will be virtual, upright and magnified.
  46. 46. Difference B/W Real & Virtual Image Real Image In it rays of light actually pass through it. It can be obtained on screen. Its distance is shown with +ve sign. It is inverted. Virtual Image a) In it rays appear coming from the place of image. b) It is only visible to eye and can not be obtained on screen. c) Its distance is shown with ve sign. d) It is upright.
  47. 47. Magnification & Sign Conventions For spherical Mirrors Optical magnification is the ratio between the size of image & size of object. M = hi = q ho p M = Magnification, hi = Height of image , ho = Height of object. Distance b/w concave mirror & image (q ) is taken +ve. Distance b/w convex mirror & image is taken ve. Focal length of concave mirror ( f ) is taken +ve. Focal length of convex mirror is taken ve .
  48. 48. Mirror Equation ( Concave Mirror) ABC and OIC are similar. AB/OI = BC/IC = p/q(i) ABF and FCD are similar. AB/DC = BF/FC = BC FC / FC = p - f / f..(ii)
  49. 49. Mirror Equation ( Concave Mirror) Comparing I & ii p/q = p f / f B.C.M pf = pq fq.(iii) Dividing both the sides of Eq:III with pqf. Pf/pqf = pq/pqf = fq/pqf. 1/q = 1/f 1/p or 1/f 1/p = 1/q. 1/f = 1/p + 1/q( Mirror Equation).