REFLECTION
Plane (flat) mirrors
LIGHT TRAVELS IN STRAIGHT LINES
HOW LIGHT BEHAVES….
When light passes from one medium to another it may
be reflected, refracted or both.
Mirror: ALL the light reflects back
Water: SOME of the light reflects back
LAW OF REFLECTION
Law of reflection states that the angle of
incidence is equal to the angle of reflection.
θi° = θr°
DEFINITIONS
1. Incidence Ray : The ray from the source. (it is the
ray from the object to the mirror.)
2. Normal: It is an IMAGINARY line drawn
perpendicular to the surface. (It bisects the mirror.)
3. Reflected Ray: The ray reflected from the mirror.
REGULAR (SPECULAR) AND
REFLECTION
Regular or specular
reflection
Ex: Mirror
DIFFUSE
Diffuse reflection
Ex: Piece of Paper
REGULAR (SPECULAR) AND
REFLECTION
Regular or specular
reflection.
DIFFUSE
Diffuse reflection.
EXTEND YOUR THINKING

Why is there a strong glare off the pavement
after it rains?
Why are glossy books sometimes hard to read?
IMAGES
•
•
•
Image – where light rays converge
Virtual image – rays do not pass through the
image. Images that are formed in locations
where light does not actually reach. Virtual
images are upright.
Real image – rays do pass through so the image
can be projected on a screen. Real images are
inverted.
PLANE MIRROR AND IMAGE FORMATION

https://www.youtube.com/watch?v=ISbrAJHdvZU
 Images are formed because light travels
in a straight line.
  Image is flipped or reversed

RAYS OFF OF A POINT OBJECT.
 Your mind traces back the reflected light
rays until they meet somewhere behind the
mirror.
RAYS OFF OF A POINT OBJECT.
Distance mirror to image = distance mirror to object
(di = do)
RAYS OFF OF A POINT OBJECT.
The image as seen by the eye is:
Because light rays
don’t actually meet in
plane mirrors, all images
produced are virtual
IMAGE OF AN ACTUAL OBJECT.
The image as seen by you is
This picture shows that you actually need a mirror that is
only half your length to be able to see your full image.
PLANE MIRROR

Where do you see your image in the mirror?

http://www.physicsclassroom.com/mmedia/optics/ifpm
.cfm
IMAGES BETWEEN TWO MIRRORS
The kaleidoscope lab show that the angle between the
mirrors and the number of images are INVERSLY
proportional.
And the relationship is A=360º/N
Here A is the angle between the mirrors and N is the #
of faces.