Lesson 8
Refraction.
This lesson involves the concept of refraction
The basic concept of the refraction of light is that as light travels through a denser medium it slows down. For example, as light travels through air and then water it slows down because water is a denser medium. Of course when we look from the side of a glass light also travels through the glass.
Many communities around the world have experience with spear fishing, including Aboriginal and Torres Strait Islander peoples, Asian peoples and indigenous groups from North America.
When discussing spear fishing in this context, we are referring to spear fishing in shallow water at the water’s surface, looking down on the fish from above.
When this happens, the fish appears to be in a different location to the reality due to refraction. The key is to aim just below the fish. (This is assuming the fish is moving away from you.)
The basic concept of the refraction of light is that as light travels through a denser medium it slows down. For example, as light travels through air and then water it slows down because water is a denser medium. Of course when we look from the side of a glass light also travels through the glass.
Many communities around the world have experience with spear fishing, including Aboriginal and Torres Strait Islander peoples, Asian peoples and indigenous groups from North America.
When discussing spear fishing in this context, we are referring to spear fishing in shallow water at the water’s surface, looking down on the fish from above.
When this happens, the fish appears to be in a different location to the reality due to refraction. The key is to aim just below the fish. (This is assuming the fish is moving away from you.)
Tips and Suggestions.
Refraction diagram
When drawing a refraction diagram, there are few conventions to adhere to.
1 As with most ray diagrams, the light needs to enter the eye. The position of the eye determines where the person is. When students complete a ray diagram, the eye should be on the side of the cup.
2 The dotted line represents what we see, not where the object actually is.
3 New arrows are drawn to show the change in direction of the light at the border between the two mediums.
4 The refraction actually occurs at two points: as the light enters and as it exits after reflection. The students will draw the light as it exits after reflection off the pencil.
Note: For the ray diagram from the side of the cup, students will need to show light refracting twice: as it moves from water to glass and then glass to air. The degree of refraction between the water and glass is small, and so the change in direction is small. Students should be given guidance with this.
When drawing a refraction diagram, there are few conventions to adhere to.
1 As with most ray diagrams, the light needs to enter the eye. The position of the eye determines where the person is. When students complete a ray diagram, the eye should be on the side of the cup.
2 The dotted line represents what we see, not where the object actually is.
3 New arrows are drawn to show the change in direction of the light at the border between the two mediums.
4 The refraction actually occurs at two points: as the light enters and as it exits after reflection. The students will draw the light as it exits after reflection off the pencil.
Note: For the ray diagram from the side of the cup, students will need to show light refracting twice: as it moves from water to glass and then glass to air. The degree of refraction between the water and glass is small, and so the change in direction is small. Students should be given guidance with this.
Information Resources.
Interactive Resources.
Colour and Refraction.
What is a rainbow? A rainbow is an arc of coloured light that occurs when light from the sun is refracted through droplets of rain. The sun must be behind the observer, and the rain in front of the observer. The Sun’s light shines through the rain droplets and refracts back to the human eye, spreading the light to reveal the colours of the spectrum.
It is useful to show the light spectrum. The colours always form in the same order:
Red
Orange
Yellow
Green
Blue
Indigo
Violet
It is useful to show the light spectrum. The colours always form in the same order:
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Reflection:
Alaska Native Knowledge Network, 2011, Alaska Science Camps, Fairs and Experiments. Retrieved 19th October 2013.
http://www.ankn.uaf.edu/publications/Alaska_Science/Spear.html
Children’s Encyclopaedia of Science, The Science of Light, When Light Bends. Retrieved 19th October 2013.
http://www.daviddarling.info/childrens_encyclopedia/light_Chapter4.html
Education Services Australia, 2013, Scootle Education, Optics and Refraction: Light Angle. Retrieved October 13trh 2013.
http://www.scootle.edu.au/ec/viewing/L1477/index.html
Kirpi.it , 2012, Lens flare Tutorial. Retrieved 19th October 2013
http://www.kirpi.it/Photo/Lens-flare-tutorial-on-how-to-avoid-create-and-control-light-reflection-and-refraction
Old Dominion University College of Sciences, 2006, How are Rainbows Made? Retrieved 30th October 2013.
http://sci.odu.edu/sci/Scire/05Edition/rainbow.html
You Tube, 2012, Mike Hunter, Dirty Jobs. Retrieved 1St November 2013.
http://www.youtube.com/watch?v=R0cD9bozobI
You Tube, Steve Spangler Science, 2010, Invisible Glass, How to Make an Object Vanish, Retrieved 19th October 2013.
http://www.youtube.com/watch?v=wlELYZJ5JF4
You Tube, 2007, Visible Light. Retrieved 30th October 2013.
< http://youtu.be/5J8iEIQBlxc >
Wiki How To Do Anything, 2013, How To Make A Rainbow. Retrieved 30th October 2013.
http://www.wikihow.com/Make-a-Rainbow
Alaska Native Knowledge Network, 2011, Alaska Science Camps, Fairs and Experiments. Retrieved 19th October 2013.
http://www.ankn.uaf.edu/publications/Alaska_Science/Spear.html
Children’s Encyclopaedia of Science, The Science of Light, When Light Bends. Retrieved 19th October 2013.
http://www.daviddarling.info/childrens_encyclopedia/light_Chapter4.html
Education Services Australia, 2013, Scootle Education, Optics and Refraction: Light Angle. Retrieved October 13trh 2013.
http://www.scootle.edu.au/ec/viewing/L1477/index.html
Kirpi.it , 2012, Lens flare Tutorial. Retrieved 19th October 2013
http://www.kirpi.it/Photo/Lens-flare-tutorial-on-how-to-avoid-create-and-control-light-reflection-and-refraction
Old Dominion University College of Sciences, 2006, How are Rainbows Made? Retrieved 30th October 2013.
http://sci.odu.edu/sci/Scire/05Edition/rainbow.html
You Tube, 2012, Mike Hunter, Dirty Jobs. Retrieved 1St November 2013.
http://www.youtube.com/watch?v=R0cD9bozobI
You Tube, Steve Spangler Science, 2010, Invisible Glass, How to Make an Object Vanish, Retrieved 19th October 2013.
http://www.youtube.com/watch?v=wlELYZJ5JF4
You Tube, 2007, Visible Light. Retrieved 30th October 2013.
< http://youtu.be/5J8iEIQBlxc >
Wiki How To Do Anything, 2013, How To Make A Rainbow. Retrieved 30th October 2013.
http://www.wikihow.com/Make-a-Rainbow