L1 seeingthings
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There are several types of light emission including incandescence from hot objects, luminescence without heating, and electric discharge through gases. The document then discusses how light travels in straight lines from an object to the eye, and how our eyes and brain work together (the eye-brain) to see light entering from our surroundings. It explains key concepts of light including reflection, spectra, wavelengths, and different parts of the electromagnetic spectrum beyond just visible light.
L1 seeingthings
- 1. Incandescence: light given off by an object because it is very hot Luminescence: Light given off by an object that has not been heated Examples: Chemiluminescence: light released during a chemical reaction Bioluminescence: light released by natural sources Electric discharge: high energy electrons reacting with gases sealed in a glass tube Flourescene: type of electric discharge where the gases emit UV light which transfers energy to phosphors that release the enrgy as light
- 3. Understanding Sight Requires Understanding Light Understanding the Eye-Brain
- 4. http://www.michaelbach.de/ot/mot_adaptSpiral/index.html The Eye & Brain (- are part of how we see.)
- 5. Meet our āEye-Brainā. We will use these often as observers on diagrams in this unit.
- 6. The tip of the candle flame emits light in all directions. But we only see the light that enters our Eye-Brain.
- 7. We don āt see light that does not enter our eyes .
- 8. We don āt see light directed away from our eyes unless it is reflected into our Eye-Brain by something.
- 9. On diagrams in this unit, we will tend to ignore all light that does not enter our Eye-Brains.
- 10. The path light takes is called a Ray . Diagrams that show how light moves from the object to the eye are called Ray Diagrams.
- 11. Light is a type of energy our eyes are sensitive to. This only tells us how we detect light but it does not tell us what light is.
- 12. Can he see the Eye-Brain ās feet?
- 13. Light travels in straight lines. This is called Rectilinear Propagation . Since no ray of light can go straight from the Eye-Brain ās feet into your eyes, you canāt see them. Experience has trained our Eye-Brain to expect that things are located in the direction that the light comes from.
- 14. Ā
- 15. Newton was the first to note that white light breaks into the colours of a rainbow when it passes through a prism. These colours are called a Spectrum.
- 16. When light from the Sun (White Light) is broken down, it ās Spectrum looks like this. White Light is made up of shades of Red, Orange, Yellow, Green, Blue, and Violet. A mnemonic for remembering the order of rainbow colours is the name Roy G Biv.
- 17. Newton noted that the individual coloured lines could not be separated further. These lines are pure colours and are identified by a frequency and wavelength number .
- 18. The atoms in sources that produce light are surrounded by electrons that can be excited to higher energy levels. As these electrons fall back to their original energy level, they give off the energy in the form of light. i.e., incandescence
- 19. There are many different ways for electrons to fall back. Each jump backdown produces a different coloured line of light. The Conceptual definition of light is; Light is produced when electrons change energy levels.
- 20. Our ears cannot hear some high sound frequencies that dogs can. Similarly, our eyes cannot āseeā some of the colours of light.
- 21. For instance, you cannot see if an iron is hot or not. Our eyes are not sensitive to the ācolourā the iron emits but our hands can feel it. The ācolourā hot irons emit is called Infra Red Radiation. Some snakes can see Infra Red Radiation.
- 22. Similarly, you cannot see water heating in a microwave oven. Our eyes are not sensitive to the ācolourā the water can absorb. The ācolourā that water is heated by is called Microwave Radiation.
- 23. The Visible Light Spectrum is a very small part of a much larger spectrum called the Electromagnetic Spectrum.
- 24. Mnemonics for Remembering the Electromagnetic Spectrum from Long to Short Wavelength Radio Waves Microwaves Infra Red Visible Spectrum Ultra Violet X-Rays Gamma Rays Raul's Mother Is Visiting Uncle Xavier's Garden Rabbits Mate In Very Unusual eXpensive Gardens Raging Martians Invade Roy G. Biv. Using X-rays & Gamma Rays
- 25. How is a wavelength defined? A wavelength is the distance between peaks on a wave. Draw and label wavelength
- 26. Reflection is the process in which light ābounces offā the surface of an object and travels in another direction.
- 27. On a ray diagram, the Object ās Location or Distance from the Eye-Brain is where all light rays appear to originate or come from.
- 28. To make the ray diagram simpler, we often only use one ray entering the eye. In this case, the Object ās Location or Distance from the Eye-Brain is where all rays originate if the eye changes position.
- 29. Atoms in Luminous Objects emit light rays in all directions produced from other energy sources.
- 30. Atoms in Non-Luminous Objects scatter the light rays from Luminous Objects in all directions. * We only see the rays that reach our Eye-Brain.
- 31. Rays of light travel from the object to the observer ās eye through a Medium . A Transparent Medium allows nearly all the rays to pass straight through unaltered. Example: Air
- 32. An Opaque Medium absorbs or scatters all the rays. Example: Your Texbook
- 33. A Translucent Medium transmits and scatters the rays. The medium indicates whether it is being illuminated but the object cannot be clearly seen. Example: Wax paper
- 34. Two eyes in front of a head can determine the object ās location better because the rays entering each eye can be used by the Eye-Brain to triangulate where the object is. This is called Depth Perception. Try the Pencil Touch Activity
- 35. Floating Finger Procedure Hold your left and right forefingers about 30 cm in front of your eyes. Hold them horizontally about 2-3 cm apart. Focus your eyes at a far point. Do not focus on your fingers. Wiggle the fingers slightly up and down. Try closing one eye at a time.
- 36. Floating Finger Did you see a piece of finger floating in the air? Explanation: The eyes are focused on a point located far away. The Eye-Brain uses two slightly different sets of rays to triangulate the distance. But we still see objects that are closer to the eyes.
- 37. The image from the left eye and the image in the right eye are combined in our brain. We see the overlap finger. The overlap is seen more clearly because it is seen by both eyes. You cannot see the floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye, image depth can only be determined by their relative size. Left Eye Image
- 38. The image from the left eye and the image in the right eye are combined in our brain. We see the overlap finger. The overlap is seen more clearly because it is seen by both eyes. You cannot see the floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye, image depth can only be determined by their relative size. Right Eye Image
- 39. The image from the left eye and the image in the right eye are combined in our brain. We see the overlap finger. The overlap is seen more clearly because it is seen by both eyes. You cannot see the floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye image depth can only be determined by their relative size. Images from Both Eyes combined in the brain
- 40. The effect of two eyes on depth perception of the Eye-Brain is also used in Magic Eye or Random Dot pictures.
- 41. The apparent Size of the object depends on the angle between rays coming from the top and bottom of the object. Large objects have a large angle between the rays.
- 42. Objects that are farther away have a small angle between rays coming from the top and bottom. This makes them appear small to the Eye-Brain Objects that are close have a large angle between the rays, and the object appears larger.
- 43. If the Eye-Brain is confused about the location of the objects, then the object ās apparent size ( dotted shapes) can be confused. The Eye-Brain may assume both objects are at the same distance. Then the distant object looks small compared to the close object.
- 44. Animals with eyes on the side of their heads can only see the object with one eye at a time. They cannot use the triangulation method to determine the object ās location. These animals must use the objectās apparent size to determine its location. Their depth perception will be poor.
- 45. The Moon Illusion is an optical illusion in which the Moon appears larger when it is near the horizon than it does when it is higher up in the sky.
- 46. One of the possible explanations of the Moon Illusion is that the eye is confused about the location of the moon and surrounding objects. Therefore, the apparent size is confused.
Editor's Notes
- #3: Somewhere between a quarter and a third of humans ā neocortex is devoted to vision. We are very good at recognizing and distinguishing fairly subtle patterns, quickly decoding printed pages, for example, or distinguishing between trees based on the pattern of their leaves or bark. We accomplish this by having a very flexible and powerful visual system.
- #4: Music to the deaf is like colour to the blind. How we see things depends on how our senses perceive things in the physical world and how our brain interprets what our senses perceive. In order to understand sight, we first have to understand what we call light in the physical world. We also have to understand how our eyes and brain work. This course will concentrate mostly on how light behaves in the physical world. The study of this is called Optics.
- #5: Open the applet MAESpiral.swf (included with permission in this folder) in a browser, if your internet connection is slow. Or go to http://www.michaelbach.de/ot/mot_adaptSpiral/index.html Instructions on how to adjust is in the Materials / Teacher Guide document. Stand beside the projected image and have the class stare at the centre of the rotating spiral for about 20 seconds. Then have them look at your face. They will notice your head either growing larger or shrinking, depending on the direction of rotation. Don't worry, it won't last. The sensation will go away after a few seconds. It demonstrates that understanding sight requires understanding the brain. Then reverse the direction and repeat. Further explanations are on the bottom of the page.
- #6: Eye-Brain graphics are by Patrick McWade < [email_address] > Used with permission
- #7: Demonstrate that we can āt see the light that does not enter our eyes by using a laser pointer. Direct the laser beam across the classroom. Make the beam visible by misting water over the beam with a hand-held atomizer. As the tiny drops of water fall through the beam, they scatter light into the studentsā eyes. This is called the Tyndall Effect. The Tyndall Effect is caused by reflection of light by very small particles in suspension in a transparent medium. It is often seen from the dust in the air when sunlight comes in through a window, or comes down through holes in clouds.
- #8: Demonstrate that we can āt see the light that does not enter our eyes by using a laser pointer. Direct the laser beam across the classroom. Make the beam visible by misting water over the beam with a hand-held atomizer. As the tiny drops of water fall through the beam, they scatter light into the studentsā eyes. This is called the Tyndall Effect. The Tyndall Effect is caused by reflection of light by very small particles in suspension in a transparent medium. It is often seen from the dust in the air when sunlight comes in through a window, or comes down through holes in clouds.
- #9: Demonstrate that we can āt see the light that does not enter our eyes by using a laser pointer. Direct the laser beam across the classroom. Make the beam visible by misting water over the beam with a hand-held atomizer. As the tiny drops of water fall through the beam, they scatter light into the studentsā eyes. This is called the Tyndall Effect. The Tyndall Effect is caused by reflection of light by very small particles in suspension in a transparent medium. It is often seen from the dust in the air when sunlight comes in through a window, or comes down through holes in clouds.
- #10: Demonstrate that we can āt see the light that does not enter our eyes by using a laser pointer. Direct the laser beam across the classroom. Make the beam visible by misting water over the beam with a hand-held atomizer. As the tiny drops of water fall through the beam, they scatter light into the studentsā eyes. This is called the Tyndall Effect. The Tyndall Effect is caused by reflection of light by very small particles in suspension in a transparent medium. It is often seen from the dust in the air when sunlight comes in through a window, or comes down through holes in clouds.
- #12: Rectilinear Propagation
- #13: Rectilinear Propagation
- #14: Rectilinear Propagation
- #15: Rectilinear Propagation
- #16: Sir Isaac Newton ās full name with title is easy to remember because of his initials (i.e. SIN).
- #17: Very good full spectrum from overhead projector ā Fisher Science Education http://www.fishersci.com/wps/portal/CMSTATIC?href=index.jsp&store=ScienceEducation&segment=scienceEduStandard&tabClicked=1 - Diffraction Grating 6x5 Roll for overhead projector S425442 Science First No.:PS-08-B Encourage students to make up their own mnemonic for remembering the order of rainbow colours. Let them know ā A mnemonic is just a way to remember simple lists ā . To show students a very good full spectrum see http://isaac.exploratorium.edu/~pauld/summer_institute/summer_day6color/color_diffraction_grating.html Note the Capital letters denote the Additive Primary colours. More on this later in ā Seeing Colour.ppt ā Isaac Newton named the colours of the spectrum that we use today. At first, he only identified 5 colours (red, yellow, green, blue, violet). He changed this to seven colours out of a mistaken belief, derived from the ancient Greeks. They believed there was a connection between the colours, the musical notes, the known objects in the solar system, and the days of the week. Newton, therefore, added Orange and Indigo to make up 7 names for the main colours of the spectrum, i.e., ROYGBIV, Red, Orange, Yellow, Green, Blue, Indigo, Violet.
- #21: Radiometer and hot iron E3.2 identify and label the visible and invisible regions of the electromagnetic spectrum
- #22: Radiometer and hot iron E3.2 identify and label the visible and invisible regions of the electromagnetic spectrum The fact that some snakes can see Infra Red Radiation gives them the advantage of being able to better perceive warm blooded prey in the dark.
- #23: Radiometer and hot iron E3.2 identify and label the visible and invisible regions of the electromagnetic spectrum
- #24: E3.2 identify and label the visible and invisible regions of the electromagnetic spectrum
- #25: E3.2 identify and label the visible and invisible regions of the electromagnetic spectrum
- #35: Animals with eyes on the side of their heads can only see the object with one eye at a time. They cannot use the triangulation method to determine the object ās location. These animals must use the objectās apparent relative size to determine its location relative to other objects. Pencil Touch Activity - Student activity to demonstrate Improved Depth Perception with two eyes. Hold a pencil in both hands about arm ās length away but with BENT ELBOWS. Close one eye and try to touch the points of the pencils together. Repeat with both eyes open. Discuss which is easier and why.
- #36: Explanation: The eyes are focused on a far point; we still see objects that are closer to the eyes. The image from the left eye and the image projected in the right eye are both combined in our brain. This is the reason why we see only a piece of the overlap finger. Whatever image overlaps is seen more clearly. You would never be able to see the same floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye, it is like looking at a picture where image depth can only be determined by the relative size.
- #38: Explanation: The eyes are focused on a far point, but we still see objects that are closer to the eyes. The image from the left eye and the image in the right eye are combined in our brain. We see the overlap finger. The overlap is more clear because it is seen by both eyes. You cannot see the floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye, it is like looking at a picture where image depth can only be determined by the relative size.
- #39: Explanation: The eyes are focused on a far point, but we still see objects that are closer to the eyes. The image from the left eye and the image in the right eye are combined in our brain. We see the overlap finger. The overlap is more clear because it is seen by both eyes. You cannot see the floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye, it is like looking at a picture where image depth can only be determined by the relative size.
- #40: Explanation: The eyes are focussed on a far point, but we still see objects that are closer to the eyes. The image from the left eye and the image in the right eye are combined in our brain. We see the overlap finger. The overlaps is more clear Because it is seen by both eyes. You cannot see the floating piece of finger with one eye closed. We are not able to see depth well with only one eye. If we use only one eye. It is like looking at a picture where image depth can only be determined by their relative size.
- #41: See L1 Random Dot Demo (MS Word Document) plus Explanatory Demo in this folder. You can demonstrate this with an overhead projector and two identical transparences of the Random dot diagram below. Hold the transparencies in clear ā Pr esentation Sheet Protectors ā in order to keep them properly aligned. You may have to trim them slightly to fit in the protectors. They should be able to slide smoothly. Start by separating the transparences so that four fusion dots are projected. Then slide them together. As the middle dots start to overlap you will see the āHiddenā circles moving toward the centre. Unfortunately, the overhead projector can only overlap and project one level at a time. It suggests the complexity of the brain which is able to overlap and view all the levels at once. An estimated 5% of the population cannot see 3-D. This may be due to the following: - poor coordination between the left and right eyes. - eyeglasses with a HUGE difference in prescription for the left and the right eyes. - Amblyopia (l a zy eye) disorder characterized by poor or indistinct vision in an eye that is otherwise physically normal. - Squint or Strabismus (eyes are not properly aligned) ~ 4% of the population. People with one eye cannot see 3-D.
- #45: Horse brain's have two halves that are not even connected. Trainers say, &quot;be sure to do both sides of the horse ā The left brain side does not communicate with his right side brain since they are not connected. http://ezinearticles.com/?Horse-Training---What-Your-Horses-Brain-Needs-From-You-For-Training-Success&id=3488528
- #46: Text http://science.howstuffworks.com/question491.htm Podcast http://podcasts.howstuffworks.com/hsw/podcasts/brainstuff/2010-04-28-brainstuff-moon-illusion.mp3
- #47: Do Not measure this . It ās a bit of a lie