10.2 handout

1. 10.2 handout 10.2 Properties of Light & Reflection

2. 10.2 Rays of Light • Reflection: The change in direction of a light ray when it bounces off of a surface • Medium: The substance through which light travels • Light travels in a straight line as long as it is moving through the same medium • Ray: A straight line with an arrowhead that shows the direction light waves are travelling

3. 10.2 10.2 Ray Tracing • Rays can be used to predict the location, size and shape of the shadows of two objects • Shadows are areas that receive fewer or no rays • The size of the object and its distance from the light source affect the size of the shadow that is cast.

4. 10.2 Fermat’s Principle • Fermat’s principle is used to predict the path light will take after reflecting from a surface or passing through a medium • “________________________________________________” • When light reflects from a surface and remains in one medium, its speed remains constant. • Thus, the path that takes the least time is also the shortest path

5. 10.2 Laws of Reflection • Incident Ray: a ray of light that travels from a light source __________________________ • Angle of Incidence: The angle between the incident ray and the normal in a _____________________ • Normal: A line that is perpendicular to a surface where a ray of light meets the ________________ • Reflected Ray: A ray that _______________________where the incident ray and the normal meet

6. 10.2 Laws of Reflection • Angle of Reflection: The angle between the reflected ray and the normal in a ray diagram • When you know the angle of incidence, you can predict the angle of reflection because they are __________

7. 10.2 Laws of Reflection • The First Law: The incident ray, the reflected ray and the normal always lie on the same plane • The Second Law: The angle of reflection ∟r, is equal to the angle of incidence, ∟i (∟r = ∟i)

8. 10.2 Skills: How to Use a Protractor

9. 10.2 Laws of Reflection

10. 10.2 Drawing Ray Diagrams Copy these steps into your notes, then do questions #1-4 on page 414

11. 10.2 Images in Plane Mirrors • Scientists call an object placed in front of a mirror the “____________” and the likeness seen in the mirror the “_____________” • Plane Mirror: A mirror with a _________________________ • If you apply the law of reflection, you can predict where the image will be and what the image will look like

12. 10.2 Images in Plane Mirrors • The brain assumes that a light ray travels in a straight line, therefore, the brain “sees” the image at some point behind the mirror • By extending the rays that reach the eye behind the mirror, we can determine where the object is “seen”

13. 10.2 Virtual Images • Virtual Images: An image formed by rays that appear to be coming from a certain position (but are not actually coming from this position); image cannot be projected on a screen • The Blue rook is virtual since you only imagine it is there (in reality, there is nothing behind the mirror)

14. 10.2 Ray Diagrams and Plane Mirrors An image has 4 characteristics (PAST): (1) Position: _____________________________________ _________________________________________________ (2) Attitude: ______________________________________ (3) Size: _________________________________________ _________________________________________________ (4) Type: ________________________________________ You can predict these characteristics by drawing the ray diagram to locate the image of the object

15. 10.2 Locating an Image in a Plane Mirror Using a Ray Diagram

18. Locating an Image in a plane Mirror Ai A i r B

19. Locating an Image in a plane Mirror Ai A r i B Bi

20. 10.2 Ray Diagrams and Plane Mirrors *The 4 characteristics of an image in a plane Mirror: (1) An image in a plane mirror is the same size as the object (2) An image in a plane mirror is the same distance from the mirror as the object (3) An image in a plane mirror has the same orientation as the object (4) An image in a plane mirror is a virtual image

21. 10.2 Do questions # 1, 2, 4, 5, 8 on page 418