- Review how the Law of Refraction bends light at the boundaries between materials

1. TODAY’S OUTCOMES: BEHAVIOR OF LIGHT - Review how the Law of Refraction bends light at the boundaries between materials - Complete activities demonstrating the Law of Refraction - Investigate the reflection and refraction of light in a prism

2. Refraction is a tougher topic than reflection - use the whole class period today if you do not understand it. You should deduce and understand a qualitative Law of Refraction (from your data in today’s and last Friday’s lab) by the time you leave today! (Quiz on Wednesday)

3. Light travels in a straight line A few basic questions from last Friday’s observations to keep in mind: Does light always travel in a straight line? cube of water air air light beam out light beam in EXCEPT at the boundary between 2 materials!

4. transmitted angle transmitted angle incident angle incident angle A few basic questions from last Friday’s observations to keep in mind: What is the incident angle and transmitted angle? cube of water air air light beam out light beam in These angles are measured with respect to the boundary; the relation between them tells you the Law of Refraction.

5. A few basic questions from last Friday’s observations to keep in mind: How does the light behave at a right angle? cube of water air air transmitted angle transmitted angle light beam in incident angle light beam out incident angle At a right angle, the light does not bend at the boundary at all - it just continues in a straight line.

6. Let’s do the right wall first. = image of fish 1) Light travels in a straight line until it hits the wall. Trish has a large fish tank with 4 fish in it. But when she tries to count them, sometimes she sees more! Use the picture below to explain how Trish can sometimes count the same fish twice (this is a view from above, and the dark lines represent the glass walls of the fish tank). Look back at the example of the object under water, and do it for both walls separately. 2) Light that strikes the wall perpendicularly just continues in a straight line. 3) Light going from water to air DECREASES in angle with respect to the boundary, and the change is bigger at when the angle is smaller. 4) Extend the transmitted lines - where they intersect is where the image will appear!

7. = image of fish Trish has a large fish tank with 4 fish in it. But when she tries to count them, sometimes she sees more! Use the picture below to explain how Trish can sometimes count the same fish twice (this is a view from above, and the dark lines represent the glass walls of the fish tank). Look back at the example of the object under water, and do it for both walls separately. 1) Light travels in a straight line until it hits the wall. 2) Light that strikes the wall perpendicularly just continues in a straight line. 3) Light going from water to air DECREASES in angle with respect to the boundary, and the change is bigger at when the angle is smaller. 4) Extend the transmitted lines - where they intersect is where the image will appear! Now the other wall

8. Trish has a large fish tank with 4 fish in it. But when she tries to count them, sometimes she sees more! Use the picture below to explain how Trish can sometimes count the same fish twice (this is a view from above, and the dark lines represent the glass walls of the fish tank). = image of fish Here, I keep only the light rays that go to Trish. NOTE: Our study of the Law of Refraction does not tell us exactly how much the light rays bend at the surface, so the location of the images we can find is an approximation. When light passes from water to air, the angle a light beam makes with the boundary decreases, as according to the Law of Refraction. Two separate surfaces at different angles form 2 separate images, so Trish sees 2 fish.

9. WHAT YOU ARE EXPECTED TO KNOW: - Light travels in a straight line EXCEPT when it crosses a boundary between materials - The dependence of the angle of transmission on the angle of incidence (Law of Refraction) - How to determine approximately where an image will be seen when refraction occurs

10. TODAY’S OUTCOMES: BEHAVIOR OF LIGHT - Review how the Law of Refraction bends light at the boundaries between materials ✓ - Complete activities demonstrating the Law of Refraction - Investigate the reflection and refraction of light in a prism