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High School. PHYSICS. InClass. by SSL Technologies. with S. Lancione. Exercise-46. Intro to Optics. Part 2 /2. Intro to Optics. PART-2 /2. In studying optics, it is convenient to classify objects into those that emit light (luminous) and those that reflect light (non-luminous):

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InClass

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  1. High School PHYSICS InClass by SSL Technologies with S. Lancione Exercise-46 Intro to Optics Part 2 /2

  2. Intro to Optics PART-2 /2 In studying optics, it is convenient to classify objects into those that emit light (luminous) and those that reflect light (non-luminous): LUMINOUS (originate light) NON-LUMINOUS or ILLUMINATED (do not originate light) Incandescent Opaque (light cannot pass through) Neon Transparent (light and images pass through) Fluorescent Translucent (light passes through, images do not) BEAM OF LIGHT: A beam of light is a "bunch" of light rays. CONVERGENCE: When rays of light come together to meet at a point, they are said to converge. DIVERGENCE: When rays of light go away from a point, they are said to diverge. MEDIUM: A medium is the material through which light travels. Optical mediums are classified according to density. The more "optically dense" a material is, the slower light travels in that medium. Click

  3. Intro to Optics THE PRIMARY COLORS Monochromatic light is light of one color. Polychromatic light is light of many colors. In everyday language we use names to represent monochromatic light such as red, orange, yellow, green, blue and violet. Furthermore, each of these colors has a variety of different shades. Collectively, all the different colors form the “light band” which is part of the “electromagnetic spectrum”. Click

  4. Intro to Optics Red, green and blue light (RGB) are called the primary colors. Adding these three primary colors together forms “white” light. Adding pairs of the primary colors form the secondary colors. Click

  5. Intro to Optics The color of an object is determined by the color (or colors) it reflects. Suppose white light shines on a red object. The object will absorb all the colors except red. Thus, it is red. Study the illustration below. Click

  6. COLOR THEORY Additive color theory Subtractive color theory Primary colors: RGB Primary colors: CMY Red – Green – Blue Cyan – Magenta – Yellow Inks Lights Cyan = Green + Blue Red = Magenta + Yellow Magenta = Red + Blue Green = Cyan + Yellow Yellow = Red + Green Blue = Cyan + Magenta White = Red + Green + Blue Black = Cyan + Magenta + Yellow Click

  7. Penumbra (grey) Umbra (black) Intro to Optics SHADOWS Shadows are formed when light is obstructed. The light may be totally obstructed thereby forming a dark shadow known as an umbra, or it may be partially obstructed thereby forming a gray shadow known as a penumbra. Click

  8. Intro to Optics For example, in diagram-A below, a point source of light encounters an obstacle (a disc) causing an umbra (total darkness). In diagram-B, a large source of light causes both an umbra and a penumbra. Note that when the source is a point, the shadow consists of an umbra (total darkness) with a well defined outline. From the side view, we have two rays (one to the top of the obstruction, one to the bottom of the obstruction) to define the shadow (the light source has no top and bottom portions). Click

  9. EXERCISES

  10. Question-1 Define the following terms: a) Beam of light A stream of photons emanating (coming from) a light source. b) Medium The material through which light travels. c) Opaque A material that blocks light (light cannot pass through). d) Transparent A material through which light and images pass through. e) Translucent A material through which light can pass through but images cannot pass through. Click Click Click Click Click Click

  11. Question-2 Define the meaning of the terms monochromatic and polychromatic light. Monochromatic is light consisting of only a single color. Polychromatic is light consisting of many colors. Click Click Click

  12. Question-3 Draw 5 rays of light that are parallel, converging and diverging. Click Click

  13. Question-4 What does RGB stand for? Red, Green and Blue. Click Click

  14. Question-5 Red Green Blue Red Green Red Blue Green Blue Yellow Cyan Magenta Fill in the primary and secondary colors in the chart below: Click Click

  15. Question-6 Define an umbra and explain how it is formed. The umbra consists of total darkness and is caused by the total obstruction of the light rays. Click Click

  16. Question-7 Define an penumbra and explain how it is formed. The penumbra consists of partial darkness and is caused by the partial obstruction of light rays. Click Click

  17. Question-8 In your own words, define light intensity. Light intensity (also known as brilliance) refers to the total number of photons emitted by a light source per second. Click Click

  18. Question-9 Sketch the electromagnetic spectrum and indicate the position of light. Click Click

  19. Question-10 In the given diagram, measure the length of the umbra and penumbra of the shadow formed by the obstruction (line). Click Click

  20. Question-11 A beam of white light strikes a glass prism producing an arrayof different colors as illustrated below. What optical phenomena does this represent? A) Specular reflection B) Total internal reflection C) Diffusion D) Dispersion By definition Click Click

  21. Question-12 The diagram below illustrates light coming from the sun to theearth with the moon in between. Which of the following statements correctly describes the shadowof the moon on the earth? I- Region Y is the penumbra II- Regions X and Z are the umbra III- Regions Y is the umbra IV- Regions X and Z are the penumbra A) I and II B) I and IV C) II and III D) III and IV Click

  22. Question-13 Blue filter The diagram below illustrates a white light source, a blue filterand a yellow object. All the colors Blue What color will the object appear? A yellow object illuminated by white light willabsorb all the colors except yellow. A bluefilter will filter all the colors except blue.Thus, when the blue light strikes the yellowobject, it will be absorbed and the objectwill appear black (since it reflects no light). A) White B) Black C) Yellow D) Blue Click Click

  23. Question-14 A green filter is placed between a red light source and an object. Red light source White object Green filter What color is the object? A) Red B) Green C) Yellow D) White E) Black A green filter will block (absorb) all colorsexcept green. Since the light source givesoff red light, the green filter will absorb thered light causing no light to fall on the object. Click Click

  24. Question-15 Three different colored objects X, Y and Z, are illuminated bythree projectors. Each projector emits a different colored light. The first projector causes object X to appear blue while theother objects appear black. The second projector causes objects X and Y to appear redwhile object Z appears black. The third projector causes objects X and Z to appear greenwhile object Y appears black. What color do the objects appear if while light is used to illuminate the objects? White Red Green Object-XObject-YObject-Z A) Blue Black Black B) Blue Red Green C) White Red Green D) White Black Red E) White Black Green Click

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