1. A Brief Look at
LIGHT

2. Light usually travels only in a straight line.
This is known as the Law of Rectilinear Propagation

3. Diagrams with Light are referred to as ray diagrams
where a ray is a single path followed by light
and a beam is a ‘bundle’ of light rays.

4. When light strikes matter
It can be affected in 3 different ways:
Transmitted: light passes through a medium
Ex. Windows
Reflected: light bounces off an object
Ex. Mirrors
Absorbed: light disappears (or certain wavelengths)
Green object  all wavelengths of light except green are absorbed

5. Classifying Objects
Objects may be classified based on how well they transmit light:
Transparent: transmits ALL light
Opaque : transmits NO light
Translucent: transmits SOME light

6. The Reflection of Light
Regular Reflection: this is reflection of light from smooth shiny surfaces.

7. Laws of Reflection Normal Incident Ray Angle of Incidence
Angle of Reflection
Reflected Ray
90o
Mirror
Point of incidence

8. Laws of Reflection
First Law: The angle of incidence is equal to the angle of reflection
Normal
Incident Ray
Angle of Incidence
Angle of Reflection
Reflected Ray
Mirror

9. Laws of Reflection Laws of Reflection
Second Law: The incident ray, reflected ray, and normal all lie on the same plane
Normal
Incident Ray
Angle of Incidence
Angle of Reflection
Reflected Ray
Mirror

10. Diffuse Reflection
Many surfaces appear to be smooth, however when they are viewed under a microscope it is clear they are not.
Because of the uneven surface, the light rays are scattered in many directions (diffused).

11. Diffuse Reflection
Further examination of a irregular surface show that they too obey the laws of reflection (ie. Angle of incidence = angle of reflection).

12. Diffuse Reflection
Most objects are made of rough surfaces (and therefore scatter light); if this did not happen, indoor lighting would not be effective.
ie. Walls, floors, ceilings, etc. scatter light in all directions, making them visible.

13. Time to practice! Complete the worksheet “kinds of reflections”
Complete the worksheet “regular and diffuse reflection”
Read text p and p
Do Questions: p. 481 #3, 5, p. 486 #1-5

14. Optical Images
An image is the representation of an object formed by the interaction of light rays.
Characteristics (LOST): Location: behind or in front of mirror Orientation: vertical (upright or inverted)
lateral (left to right)
Size: bigger, smaller or same size as object
Type : Real – when the reflected rays converge in front of the mirror to produce an image (can be seen on a screen)
or Virtual – when the reflected rays converge behind the mirror (cannot be reflected onto a screen)

15. Images Formed in Plane Mirrors
How do I see an image of the arrow??

16. Images Formed in Plane Mirrors
Light from the arrow hits the mirror

17. Images Formed in Plane Mirrors
..and is reflected into my eye

18. Images Formed in Plane Mirrors
The image!!
..and my brain ‘sees’ the image where the light appears to have come from!

19. Characteristics of a PLANE MIRROR Image
Characteristics in a plane mirror are always: Location: behind the mirror the same distance from the mirror as the object
Orientation: image is upright, and laterally inverted
Size: same size as object
Type : virtual
(In you book it’s SALT (Size, Attitude, Location, Type))

20. Homework Time! Complete Worksheet “Plane Mirrors and their Images”
Complete Worksheet “Drawing Images in a Plane Mirror”
Read pg
Do Questions pg. 493 #1-7, 9
REMINDER: QUIZ on Tuesday!!! (electromagnetic spectrum, sources of light, law of reflection and images in a plane mirror)