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Color Deficiency

Color Deficiency. Why do we see certain colors?. We perceive only the reflected colors. Color by Transmission. The color of a transparent object is due to the color that it transmits The material that absorbs colored light is known as pigment. Pigment.

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Color Deficiency

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  1. Color Deficiency

  2. Why do we see certain colors? • We perceive only the reflected colors.

  3. Color by Transmission • The color of a transparent object is due to the color that it transmits • The material that absorbs colored light is known as pigment.

  4. Pigment • Selectively absorbs some light frequencies while other frequencies are emitted. • This process of absorbing light is known as a subtractive process

  5. Total Reflection or Absorption • White is a combination of all colors of light being reflected. • Black is the absence of light, all light is being absorbed.

  6. Transmitted VS Absorbed http://cnx.org/content/m15131/latest/

  7. Primary colors of Pigment • As a child you were taught that red, yellow & blue were the primary colors, however cyan, magenta and yellow are the most useful when color mixing. http://home.att.net/~RTRUSCIO/MIXITUP.htm

  8. Primary Colors of Pigment • Mix red, green and blue paint and the result is muddy brown. • Color printing is achieved by using magenta, cyan, yellow and black ink http://home.att.net/~B-P.TRUSCIO/COLOR.htm

  9. Subtractive Primary Colors of Pigment • Pigments reflect the color they are as well as other colors to either side of them on the visible spectrum. Subtractive PrimariesCMYKCyan, Magenta and YellowPrint

  10. Cyan is light with a wavelength between green and blue or a combination of green and blue light. • Cyan pigment will absorb the red and reflect green and blue or cyan colored light.

  11. Lenses • A thin lens consists of a piece of glass or plastic, ground so that each of its two refracting surfaces is a segment of either a sphere or a plane • Lenses are commonly used to form images by refraction in optical instruments (cameras, telescopes, etc.)

  12. Lenses - Refraction There two types of lenses - Convex and Concave

  13. Thin Lens Shapes (Convex) • converging lenses • They have positive focal lengths • They are thickest in the middle • Produces a real image- refracted light rays do cross at the focal point

  14. More Thin Lens Shapes (Concave) • diverging lenses • They have negative focal lengths • They are thickest at the edges • Produces a virtual image- refracted light rays do not cross

  15. Atmospheric Refraction and Sunsets • Light rays from the sun are bent as they pass into the atmosphere • It is a gradual bend because the light passes through layers of the atmosphere • Each layer has a slightly different index of refraction • The Sun is seen to be above the horizon even after it has fallen below it

  16. Atmospheric Refraction and Mirages • A mirage can be observed when the air above the ground is warmer than the air at higher elevations • The rays in path B are directed toward the ground and then bent by refraction • The observer sees both an upright and an inverted image

  17. Eyes and Eyeglasses What type of lens do we have in our eyes? Why do we have problems seeing? What can we do to correct those problems?

  18. SEEING LIGHT - THE EYE • Cornea - does most of the focusing • Iris - has the eye color and controls light intensity • Pupil - the hole in the eye • Lens - does remainder of focusing • Retina - location of light sensors, has rods and cones center of vision, predominantly cones • Fovea - • Blind spot - optic nerve exit, no light sensors

  19. Nearsightedness Also called myopia, defect of vision in which far objects appear blurred but near objects are seen clearly. The image is focused in front of the retina rather than upon it. Corrective eyeglasses with concave lenses compensate for the refractive error and help to focus the image on the retina.

  20. Nearsightedness Reflected light enters eye Focal point

  21. Farsightedness also known as hyperopia A condition in which far objects can be seen easily but there is difficulty in near vision. The image is focused behind the retina of the eye rather than upon it. Corrective eyeglasses with convex lenses compensate for the refractive errors.

  22. Farsightedness Focal point behind retina Reflected light enters eye

  23. Astigmatism…pronounced as: stigmatizm A type of faulty vision caused by a non-uniform curvature in the refractive surfaces-usually the cornea, less frequently the lens-of the eye. As a result, light rays do not all come to a single focal point on the retina. Instead, some focus on the retina while others focus in front of or behind it. Vision is blurred. A special cylindrical lens is placed in the out-of-focus axis to correct the condition.

  24. Astigmatism

  25. Mirrors any shiny smooth surface three types of mirrors convex, concave, and plane

  26. Mirror Symbols f    = focal length p   = distance between object and mirror q   = distance between image and mirror ho = height of object hi  = height of image M = magnification = hi / ho http://sol.sci.uop.edu/~jfalward/reflection/reflection55.html

  27. Notations and Flat Mirror • The object distance is the distance from the object to the mirror or lens • Denoted by p • The image distance is the distance from the image to the mirror or lens • Denoted by q • The lateral magnification of the mirror or lens is the ratio of the image height (h ’) to the object height (h) • Denoted by M(=h’/h)

  28. Types of Images for Mirrors and Lenses • A real image is one in which light actually passes through the image point • Real images can be displayed on screens • A virtualimage is one in which the light does not pass through the image point • The light appears to come (diverge) from that point • Virtual images cannot be displayed on screens

  29. Real Image Image that is formed by converging light rays that can be displayed onto a screen. EX: rays of light from an overhead projector Virtual Image Image formed through reflection or refraction. Can be seen by the observer, but cannot be projected onto a screen EX: plane mirror image Mirror Images

  30. More About Images Image distance Object distance • To establish where an image is formed, it is always necessary to follow at least two rays of light as they reflect from the mirror. The image formed by the flat mirror is a virtual image

  31. Flat Mirror p=q! • Simplest possible mirror • Properties of the image can be determined by geometry • One ray starts at P, follows path PQ and reflects back on itself • A second ray follows path PR and reflects according to the Law of Reflection

  32. Properties of an Image Formed by a Flat Mirror • The image is as far behind the mirror as the object is in front • p = q • The image is unmagnified, M=1 • The image is virtual • The image is upright • It has the same orientation as the object • There is an apparent left-right reversal in the image http://sol.sci.uop.edu/~jfalward/reflection/reflection55.html

  33. Application – Day and Night Settings on Car Mirrors • With the daytime setting, the bright beam of reflected light is directed into the driver’s eyes • With the nighttime setting, the dim beam (D) of reflected light is directed into the driver’s eyes, while the bright beam goes elsewhere

  34. Spherical Mirrors • A spherical mirror has the shape of a segment of a sphere • A concave spherical mirror has the silvered surface of the mirror on the inner, or concave, side of the curve • A convex spherical mirror has the silvered surface of the mirror on the outer, or convex, side of the curve

  35. Concave Mirror, Notation • The mirror has a radius of curvature of R • Its center of curvature is the point C • Point V is the center of the spherical segment • A line drawn from C to V is called the principle axis of the mirror • I is the image point

  36. Image Formed by a Concave Mirror, cont. • h ’ is negative when the image is inverted with respect to the object

  37. Focal Length • Incoming rays are essentially parallel • In this special case, the image point is called the focal point • The distance from the mirror to the focal point is called the focal length • The focal length is ½ the radius of curvature f = R/2

  38. Focal Point and Focal Length, cont. • The focal point depends solely on the curvature of the mirror, not by the location of the object • With f=R/2, the mirror equation can be expressed as

  39. Sign Conventions for Mirrors

  40. Focal Length Shown by Parallel Rays

  41. Concave Mirror The center of this mirror curves away from you. This means that with the law of reflection the reflected light rays will cross producing a real image.

  42. Images produced with Concave Mirror • do = C : real inverted image, same size • do = F : no image is seen If object is past C: Real, inverted, reduced image is formed If object is between C and F: real, inverted, large image is produced If in front of F: virtual, upright, enlarged image is produced F C

  43. Convex Mirrors • A convex mirror is sometimes called a divergingmirror • The rays from any point on the object diverge after reflection as though they were coming from some point behind the mirror • The image is virtual because it lies behind the mirror at the point where the reflected rays appear to originate • In general, the image formed by a convex mirror is upright, virtual, and smaller than the object

  44. Image Formed by a Convex Mirror

  45. Convex Mirror curves outwards in the middle produces an image that is virtual, upright and smaller than the object Reflected light rays never meet so they cannot produce a real image

  46. Objects in mirror are closer than they appear The Mirror Equation    1/do + 1/di = 1/f      (1)-------------------------- Convex:  f  is negative-------------------------- Object distances are always positive for all types of mirrors. do is positive  ------------------------------ 1/di= 1/f - 1/do      (2)        = neg - pos        = negative     di is negative Magnification Equation:         M = -di / do       (3)------------------------------------ M = -(negative)/positive      = positiveImage is upright-----------------------------------From (2), we see that themagnitude of 1/di is alwayslarger than 1/do, so themagnitude of di is alwayssmaller than do:M is always less than onefor a convex mirror. http://sol.sci.uop.edu/~jfalward/reflection/reflection55.html

  47. Convex Mirror

  48. Concave vs. Convex

  49. Ray Diagrams • A ray diagram can be used to determine the position and size of an image • They are graphical constructions which tell the overall nature of the image • They can also be used to check the parameters calculated from the mirror and magnification equations

  50. Drawing A Ray Diagram • To make the ray diagram, you need to know • The position of the object • The position of the center of curvature • Three rays are drawn • They all start from the same position on the object • The intersection of any two of the rays at a point locates the image • The third ray serves as a check of the construction

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