Optics is the study of light and how light behaves.

Transcription

1 Optics : Day 1 Goals : 1. Distinguish between non-luminous and luminous light sources 2. Describe how light is produced through one of 7 different manners 3. Define light Feb 6 1:28 PM Optics is the study of light and how light behaves. What is light? Sep 7 2:25 PM 1

2 Light is energy that we can see with our eyes. Through observation scientists have come up with several important properties of visible energy. Light can come from a wide variety of sources but all light can be broken down into two groups. Think of some differences between light from the moon and light form the Sun Sep 7 2:26 PM Two groups of light sources Luminous sources (produce own light) Eg. Sun, stars, glowing lamps, fireflies Non luminous sources (does not produce own light BUT reflects light) Eg. Moon, people, tree Sep 15 8:58 AM 2

3 Sources of Light We will be exploring 7 different sources of light. Use the textbook to complete a summary table for the following sources of light : Incandescence, electrical discharge, phosphorescence, fluorescence, chemiluminescence, bioluminescence, triboluminescence The headers for the table should be : Type of light source (from above), How is the light produced?, Key qualities, example of source Key qualities should be a few words that summarize what defines that type of light source... for example I would use "high temperature" for incandescence. Leave space in your table in case you missed any key points Sep 15 8:56 AM Type of Luminous Source How is the light produced? key characteristics example of light source incandescence electrical discharge phosphorescence fluorescence chemiluminescence bioluminescence trioboluminescence Feb 7 12:43 PM 3

4 optics 1.notebook Incandescence Heat energy changed into light energy (so hot it glows) Eg. Stove element, candle, sparks, light bulb (old fashioned), fireworks Inefficient 5 10% of energy converted to light **Bunsen Burner and Metal** Sep 15 9:00 AM Electrical Discharge Sep 15 9:02 AM 4

5 An electrical current passing through gas gives energy to outer electrons. These electrons release energy, in the form of light, when the electron returns to ground state. Eg. Neon, lightning Different gases = different colours **Gas Tubes** Sep 15 9:02 AM Phosphorescence Sep 15 9:04 AM 5

6 Phosphors (a chemical) absorb energy (UV) and release visible light the energy can be stored for various time periods allowing the light to be released even after the UV source is removed Eg. Glow in the dark materials watch dials, stickers ** UV beads** Sep 15 9:06 AM Fluorescence Materials that absorb UV and immediately release visible light Eg. Fluorescent dyes in laundry soap, highlighters, Fluorescent lights use electric discharge in mercury vapour and tube coated in fluorescent material to create light 5 times more energy efficient than incandescent Sep 15 9:07 AM 6

7 Chemiluminescence Production of light via a chemical reaction often referred to as cold light Eg. Glow sticks Produce almost no heat cold light! One chemical in glass vial in centre, other outside the vial bending breaks the vial so the chemicals can mix **Glycerin and Potassium Permanganate** Sep 15 9:08 AM Bioluminescence Chemiluminescence in living organisms Eg. Bacteria, fungi, marine inverts, fish, glow worms and fireflies Used to lure prey, attract mates, protect from predators Sep 15 9:10 AM 7

8 Triboluminescence Sugar crystals being scratched or rubbed will release energy as light light is released when chemical bonds are broken seen in Scotch brand tape **Winter green lifesaver activity** Sep 15 9:12 AM Light Emitting Diode The movement of electrons in a semiconductor that releases light (how we re not quite sure???) Eg. Christmas lights, traffic lights, car lights Sep 15 9:14 AM 8

9 Summary Tasks : 1. Complete your table summarizing the sources of light for your notes 2. Answer the following questions (full sentences) in your notebook : a) Phosphorescence and Fluorescence are both sources of light in which ultraviolet light converts into visible light. What is the difference between these two sources. b) Distinguish between how an incandescent light bulb and a fluorescent tube creates light. c) Do fluorescent whiteners in detergents really make clothes cleaner? Sep 7 2:38 PM Sep 7 3:11 PM 9