8594774 optical-illusions

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8594774 optical-illusions

  1. 1. OPTICALOPTICAL ILLUSIONSILLUSIONS
  2. 2. INDEXINDEX  DEFINITION  TYPES OF OPTICAL ILLUSIONS  PERCIEVING OPTICAL ILLUSIONS- 1. Role of eye 2. Role of Brain • FACTORS CAUSING OPTICAL ILLUSIONS • NATURAL OPTICAL ILLUSIONS
  3. 3. An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source. DEFINITITONDEFINITITON
  4. 4. When we experience a visual illusion we may see something that is not there or fail to see something that is there or even see something that different from what is there! Because of this dissociation between perception and reality, visual illusions demonstrate the ways in which the brain can fail to recreate the physical world. By studying these failings, we can learn about the computational methods that the brain uses to construct visual experience.
  5. 5. TYPES OF OPTICALTYPES OF OPTICAL ILLUSIONSILLUSIONS There are 3 main types of optical illusions  LITERAL OPTICAL ILLUSIONS  PHYSIOLOGICAL OPTICAL ILLUSIONS  COGNITIVE OPTICAL ILLUSIONS
  6. 6. I. LITERAL OPTICAL ILLUSIONS Literal optical illusions are those illusions that create images that are different from the objects that make them.
  7. 7. PHYSIOLOGICAL ILLUSIONS  Physiological illusions are presumed to be the effects on the eyes or brain of excessive stimulation of a specific type - brightness, tilt, color, movement, etc. The theory is that stimuli have individual dedicated neural paths in the early stages of visual processing, and that repetitive stimulation of only one or a few channels causes a physiological imbalance that alters perception
  8. 8. III.III. COGNITIVE ILLUSIONSCOGNITIVE ILLUSIONS Cognitive illusions are assumed to arise by interaction with in-built assumptions or 'knowledge' of the world, leading to "unconscious inferences", an idea first suggested in the 19th century. Cognitive illusions are commonly divided into:  AMBIGUOUS ILLUSIONS  DISTORTING ILLUSIONS PARADOX ILLUSIONS OR FICTION ILLUSIONS
  9. 9. Ambiguous illusions are pictures or objects that elicit significant changes in appearance. Perception will 'switch' between the alternates as they are considered in turn as available data does not confirm a single view. The Necker cube is a well known example. Another instance is the Rubin vase.   1. AMBIGUOUS ILLUSIONS
  10. 10. RUBINVASEILLUSION 
  11. 11. Distorting illusions offer distortions of size, length, or curvature.Example:cafe wall illusion 2. DISTORTING ILLUSIONS
  12. 12. Paradox illusions offer objects that are paradoxical or impossible.example:Penrose triangle Penrose triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join.   3. PARADOX ILLUSIONS OR FICTION ILLUSIONS
  13. 13. PERCIEVINGPERCIEVING OPTICAL ILLUSIONSOPTICAL ILLUSIONS
  14. 14. THE HUMAN EYETHE HUMAN EYE
  15. 15. STRUCTURE OF EYESTRUCTURE OF EYE WALLS OF EYE Tunica Fibrosa Tunica Vasculosa Retina Sclera Cornea choroid Ciliary body Iris Photo- receptor cells Bipolar cells Ganglion cells ConesRods Optic nerve
  16. 16. VISUAL PERCEPTION
  17. 17. ROLE OF BRAINROLE OF BRAIN  Retina isresponsible for converting light signals to neural signals.  Optic nerve starts at a point in retina called the blind spot  Optic chiasm:-the optic nerve meets here in the first part of the brain  The OCCIPITAL LOBE located posterior in the brain deals with vision
  18. 18. FACTORS CAUSING OPTICALFACTORS CAUSING OPTICAL ILLUSIONSILLUSIONS Following are the factors causing optical illusions 1.Colour 2.Eye Structure 3.Depth and distance 4.Past experience 5.Lines and curves
  19. 19. 1) COLOUR
  20. 20. 2) EYE STRUCTURE 1.Arrangement of rods and cones on retina 2.Peripheral vision
  21. 21. 3) DEPTH AND DISTANCE
  22. 22. 4) PAST EXPERIENCE African tribe
  23. 23. 5) LINES AND CURVES
  24. 24. NATURAL OPTICALNATURAL OPTICAL ILLUSIONSILLUSIONS
  25. 25. RAINBOWS
  26. 26. Auroras are natural light displays in the sky, usually observed at night, particularly in the polar zone. They typically occur in the ionosphere AURORAS
  27. 27. A mirage is a refraction phenomena in which the image of some object appears displaced from its true position. A common example of a mirage is the appearance of water some distance down the highway on a hot summer day. MIRAGE
  28. 28. SEEING ISSEEING IS DECEIVINGDECEIVING
  29. 29. HOW MANY BLACK DOTS CAN YOU SEE IN THIS PICTURE
  30. 30. There are…..NONE And….
  31. 31. BY THE WAY, HOW MANY LEGSBY THE WAY, HOW MANY LEGS DOES THIS ELEPHANT HAS?DOES THIS ELEPHANT HAS?
  32. 32. REFERENCESREFERENCES Textbook of Medical Physiology by Arthur .C. Guyton,John..E.Hall Elements of chordate anatomy By Charles K. Weichert Biology textbook for class XII-NCERT www.physorg.com www.michaelbach.de IMAGES: www.google.com

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