TOPIC 4.3
SNC2P

 Today we will learn that:
 colours of light can be added together to form a variety of colours through two investigations.
 Pigments can subtract colours from light.

 WHAT COLOURS DID YOU
OBSERVE IN YESTERDAY’S
ACTIVITY?
 IF YOUR HAVE A CELL
PHONE, PLEASE TAKE IT
OUT NOW ... ITS TIME TO
TEXT IN YOUR
OBSERVATIONS!
 TEXT YOUR RESPONSES TO
... 37607

(Textbook P.300)
FILTER
COLOURS
RED
GREEN
BLUE
RED +
GREEN
RED + BLUE
GREEN +
BLUE
RED + BLUE
+ GREEN
OBSERVATIONS
ACTIVITY 4.4: TRICKING THE EYE
ACTIVITY: SUNLIGHT & PADDLE
COLOURS
RED RED
GREEN
BLUE
GREEN
BLUE
YELLOW
MAGENTA (PURPLE)
CYAN (TURQUOISE)
WHITE

 That the millions of colours on a computer monitor or
TV screen are produced with ONLY ...
3
C O L O U R S !
!

 Your eyes have only 3 types of cells that can recognize millions of colours.
 When you observe a colour, it is because different combinations of these cells are stimulated.
 A TV screen uses a system of only three colours to create the effect of many different colours, just like the cells in your eyes.

 PRIMARY COLOURS:
 Three colours that can be combined to create any other colour.
 Can be additive or subtractive.
RED GREEN BLUE

 ADDITIVE PRIMARY COLOURS ARE:



Red
Green
Blue
 These three colours of light are also known as primary colours.

 Creating different colours of light depend on the additive colour theory.
 When all 3 primary colours are combined, they make
white light.

 By combining only two of the primary colours, you will make a secondary colour.
 These are:
 Yellow
 Cyan
 Magenta

 Colours that are directly across from each other are complementary colours.
 Red & cyan
 Green & magenta
 Blue & yellow

When an object absorbs a colour, it removes (or subtracts) it from the beam of light. The colours of most of the objects that you observe every day are the result of subtracting colours.
There are three subtractive primary colours: cyan,
magenta, and yellow. A variety of combinations of these three colours can subtract light from white light to produce nearly any colour.
Magenta, cyan, and yellow films subtracting colours from white light.
What do you see when these three overlap?


The colours produced by subtracting equal amounts of two of the three subtractive primary colours are called subtractive secondary colours .
The subtractive secondary colours are the same as the three additive primary colours (red, green, and blue) .


When the three subtractive primary colours are added together and subtracted from white light, you get black. The “code” for black is K so as not to be confused with blue.

 If a colour is absorbed, it will not make it to your eye. You only see the reflected colours.
 Paint and pigment manufacturers mix all three of the primary subtractive colours in varying degrees to make any range of colours reflect from a surface.

Yellow M agenta Cyan Black

The COLOUR WHEEL shows how all the colours are related.

Tertiary colours are formed by mixing the secondary colours. The resulting colours are yellow-green, orange,
crimson, cobalt, and turquoise.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

The subtractive primary colours cyan, magenta, and yellow are the same as the additive secondary
colours.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

The additive primary colours red, green, and blue are the same as the subtractive
secondary colours.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

The colours that are directly across from each other on the colour wheel are
complementary colours.
When you add complementary colours, the result is white.
When you subtract complementary colours, the result is black.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

Diagrams can be used to show how colours are subtracted from white light when it hits a film of a certain colour.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

ACTIVITY 4.6
(Textbook P.301)
SUBTRACTING COLOUR WITH FILMS & WITH YOUR EYES





THREE parts to the activity.
Part A:
 At stations.
 Please record your observations on your handout.
Part B:
 At your desk in groups of 2 or 3.


Pg. 301 “What To Do”. Do # 6 and 7.
Please record your observations on your handout.
Part C:
 Answer the questions on the handout.
HAND-IN YOUR ACTIVITY HANDOUT AT THE END OF CLASS.
HOMEWORK: Handouts on Addition & Subtractive Colours

 Place the YELLOW film over the colour wheel found on page 299 of the textbook.
 Beside each colour on your list (see handout), write the colour that it appears to be after the YELLOW film was placed over it.
 Go to the next colour station
 There are 4 colour stations to complete.

 Place the RED film over the colour wheel found on page 299 of the textbook.
 Beside each colour on your list (see handout), write the colour that it appears to be after the RED film was placed over it.
 Go to the next colour station
 There are 4 colour stations to complete.

 Place the ORANGE film over the colour wheel found on page 299 of the textbook.
 Beside each colour on your list (see handout), write the colour that it appears to be after the ORANGE film was placed over it.
 Go to the next colour station
 There are 4 colour stations to complete.

 Place the GREEN paddle over the colour wheel found on page 299 of the textbook.
 Beside each colour on your list (see handout), write the colour that it appears to be after the GREEN paddle was placed over it.
 Go to the next colour station
 There are 4 colour stations to complete.