Light and Optics

Transmission, Absorption, and Reflection of LIGHT

Light transmission: • The process in which light travels through a medium

(eg. water, air etc.)

• If light is transmitted through a medium (eg. water, glass) so that the objects are visible on the other side the medium is called: TRANSPARENT

• If light is transmitted through a medium (eg. wax paper, frosted glass) the light is scattered and the objects are partly visible on the other side, the medium is called: TRANSLUCENT

Transmission, Absorption, and Reflection of LIGHT

• Absorption: light is taken in by an object and converted to other forms of energy (thermal)

• Reflection: the bouncing back of light from an object (eg. light bounces of a mirror)

OPAQUE: absorbing OR reflecting ALL transmitted light so that objects are notvisible on the other side (eg. wood, textbook, stone, etc.)

The Reflection of Light

•Last point for the lesson … reflection occurs off any surface.

•But the reflection will be different for smooth surfaces like a mirror or still water compared to a rough surface like a cupboard or the wall.

•Reflection from a smooth surface is called regular or specular reflection.

•Reflection from a rough surface is called diffuse reflection.

•The rules for diffuse reflection are still the same … the angle of incidence equals the angle of reflection (but the normals are not all pointing in the same direction)..

Finding an image

in a plane mirror:

• Depending on your object select one or more points on the object (example:top = point #1 and bottom = point #2)

• Measure from point #1 perpendicular to the mirror. • Take that measurement and measure the same

amount along the same perpendicular line on the other side of the mirror. This is now the top point of your image. Call it point #3.

#1

#2

#3

Finding an image

in a plane mirror (continued)

• Do the same for point #2 as you did for point #1.

• Call the new image point, point #4.

• Join point #3 to point #4 to form your image (in this example it is an arrow).

#1

#4

#3

#2

Finding an Image in a Plane Mirror

Finding an image in a plane mirror using a ray diagram – finding a single

point like a small bulb

mirror

object

AB

image

Where is the image of the

lamp?Hint: Your eyes do not know that the light has been reflected at the

mirror and think that the object is where the light is

coming from!

Write a statement about the object to mirror and image to mirror distances

mirror

object

AB

image

You write in here a statement about this line

Distance from object to mirror = Distance from image to mirror

Line between object and image is at right angles to mirror

What have we

discovered?

Ok check how good you are. Place a real mirror on the mirror line and look

into the mirror at the object.

mirror

object

AB

image

Real mirror

Look from here

Magic eh!

Finding an image in a plane mirror using a ray diagram – finding a

bigger object like an balloon

mirror

object

AB

image

Where is the image of the

top of the flower?

Now that you have found where the top of the

flower is, repeat the rays from the bottom of the

vase! Then you will find out where the bottom of

the vase is.

Another example: