is10_sb_unit_d

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If you have ever walked through a meadow on a warm summer evening, you may have seen flickering light produced by fireflies. Fireflies attract mates by flashing light in a specific pattern. Fireflies produce their light by a chemical reaction (Figure 10.23). D5 Quick Lab Sources of Light Emission (Teacher Demonstration) Purpose To observe several methods of producing light Materials & Equipment Some or all of: • light bulb connected to a dimmer switch • beaker • tonic water • overhead projector CAUTION: Do not shine bright light into anyone’s eyes. Incandescent light sources can become very hot. Do not touch the bulbs or block air flow around the light bulbs. Keep all electrical devices and metals away from the plasma ball. Procedure • black light • pliers • wintergreen candy • glow-in-the-dark paints • plasma ball 1. Work with a partner or in your group to predict all the possible sources that can produce light. Record your predictions in your notebook. 2. Observe as your teacher demonstrates various sources of light. After each demonstration, record your answer for questions 3 and 4. Sample Demonstrations A. A clear light bulb containing a filament is connected to a dimmer switch. Observe as the switch is turned up and down. B. Fill the beaker with tonic water, and place it on an overhead projector. Hold a black light near the beaker. Then, apply clear sunscreen to the outside of the beaker and hold the black light near the beaker again. Figure 10.23 Fireflies emit light from a light-producing organ in their abdomen. Figure 10.24 A plasma ball C. Use a pair of pliers to crush wintergreenflavoured candy in a darkened room. D. Use glow-in-the-dark paints to write a message on a piece of paper. Hold the paper near a light source. Remove the light source, darken the room, and observe the message. E. Turn on a plasma ball, and touch it. Questions 3. For each demonstration, was the light produced by high temperature, electricity, chemical reaction, or some combination of these? 4. For each demonstration, explain in a sentence or two why or how light is produced. 5. Return to your predictions from step 1. How do the sources of light demonstrated apply to your predictions in step 1? Light is part of the electromagnetic spectrum and travels in waves. 393
WORDS MATTER “Incandescent” has its roots in the Latin word incandescere, which means to become white with heat. (a) (b) Figure 10.25 (a) An incandescent bulb and (b) a compact fluorescent bulb. The fluorescent bulb uses a quarter the energy of the incandescent bulb but contains more toxic materials than an incandescent bulb. 394 UNIT D Light and Geometric Optics Sources of Light Light produced by the Sun or other stars is called natural light. Light produced through human technology is called artificial light. Think about how many times you flip on a switch and the light immediately comes on. In most cases, the light bulb that lights up is either a fluorescent bulb or an incandescent bulb. Incandescent Light Incandescent light is light that is produced by an object, such as a metal, that is at a very high temperature. Inside an incandescent light bulb is a filament, which is a thin piece of wire (Figure 10.25(a)). When you turn on an incandescent bulb, electric current flows through the filament, heating it to an extremely high temperature. The filament emits light as a way to release some of its energy. The light you see from an incandescent bulb is the filament glowing. Incandescent bulbs are extremely inefficient. Only 5 percent of the electrical energy used in an incandescent light bulb is converted to light. The rest of the energy is released as heat. Because they waste more energy than fluorescent lights, incandescent bulbs are being eliminated from widespread use. Fluorescent Light Fluorescent light is light emitted by some substances when they are exposed to electromagnetic radiation. A fluorescent light bulb is a glass tube filled with a small amount of a gas such as mercury vapour. The inside of the bulb is coated with a white powder called a phosphor. A phosphor is a substance that glows after being exposed to energized particles. As electric current passes through a fluorescent bulb, it energizes the atoms in the gas, which then emit ultraviolet radiation. The ultraviolet radiation strikes the phosphor on the inside of the bulb, which then glows and emits light (Figure 10.25(b)). Compact fluorescent light bulbs are much more efficient than incandescent light bulbs, but they still release up to 80 percent of their energy as heat (Figure 10.26). Figure 10.26 A researcher testing the endurance of fluorescent light tubes
Page 1 and 2: UNIT D Light travels through colour
Page 3 and 4: Exploring These doctors are examini
Page 5 and 6: 0 Light is part of the electromagne
Page 7 and 8: 10.1 Here is a summary of what you
Page 9 and 10: During Reading Graphics Support Tex
Page 11 and 12: Uses of the Electromagnetic Spectru
Page 13 and 14: light source white light prism scre
Page 15 and 16: Figure 10.19 The subtractive theory
Page 17 and 18: DI Key Activity D4 Quick Lab Seeing
Page 19: 10.2 Here is a summary of what you
Page 23 and 24: During Reading Get the Picture Even
Page 25 and 26: Figure 10.36 Plasma screens use flu
Page 27 and 28: D7 Quick Lab Analyzing Light Source
Page 31 and 32: Figure 10.42 Light rays travel away
Page 33 and 34: Suggested Activities • • D10 Qu
Page 35 and 36: D11 Inquiry Activity Shadows and Ra
Page 37 and 38: Investigating 410 UNIT D Light and
Page 39 and 40: 10 CHAPTER REVIEW ACHIEVEMENT CHART
Page 41 and 42: 11 Ray diagrams model the behaviour
Page 43 and 44: 11.1 Mirrors Here is a summary of w
Page 45 and 46: During Reading Diagrams Require Spe
Page 47 and 48: Suggested Activity • D16 Problem-
Page 49 and 50: 422 object ray 1 ray 2 image Figure
Page 51 and 52: Practice Problems 1. A microscope p
Page 53 and 54: Figure 11.16 Parallel light rays ap
Page 55 and 56: D13 Quick Lab Plane Mirror Reflecti
Page 57 and 58: DI Key Activity D15 Inquiry Activit
Page 59 and 60: D16 Problem-Solving Activity Laser
Page 63 and 64: Figure 11.30 The spoon appears to b
Page 65 and 66: Practice Problems 1. The speed of l
Page 67 and 68: Figure 11.36 This diamond is colour
Page 69 and 70: Suggested Activity • D19 Inquiry
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D18 Inquiry Activity Refraction Mea
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D20 Design a Lab Transmitting Light
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11.3 Lenses Here is a summary of wh
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WORDS MATTER The word “lens” is
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object ray 2 F ray 1 image Figure 1
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Suggested Activity • D25 Inquiry
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Practice Problems 1. A convex lens
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D23 Skill Builder Activity Drawing
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D25 Inquiry Activity Convex Lens Im
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11.3 CHECK and REFLECT Key Concept
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11 CHAPTER REVIEW ACHIEVEMENT CHART
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2 Optical devices help us see farth
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12.1 Here is a summary of what you
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WORDS MATTER “Pupil” is derived
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Suggested Activity • D28 Inquiry
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(a) near-sightedness (b) near-sight
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(a) (b) Figure 12.17 (a) Loss of th
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D28 Inquiry Activity Sheep Eye Diss
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DI Key Activity CASE STUDY D29 STSE
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12.2 Here is a summary of what you
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Figure 12.24 This portable imaging
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Suggested STSE Activity • D34 Dec
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During Writing Evaluating Informati
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WORDS MATTER The word “laser” i
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Figure 12.39 Long rows of solar cel
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D33 STSE Decision-Making Analysis S
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12.2 CHECK and REFLECT Key Concept
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12 CHAPTER REVIEW ACHIEVEMENT CHART
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D UNIT • Electromagnetic spectrum
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D UNIT Task How Much Light Is Too M
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D UNIT Review Key Terms Review 1. C
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D UNIT Review (continued) 35. (a) D
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D UNIT Review (continued) 62. Descr
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