Everything Science Grade 12

10.4 CHAPTER 10. COLOUR

Example 9: Primary pigments

QUESTION

I have a ruler which reflects red light and absorbs all other colours of light.

What colour does theruler appear in white light? What primary pigments

must have been mixed to make the pigment which gives the ruler its colour?

SOLUTION

Step 1 : What is being asked and what are we given?

We need to determinethe colour of the ruler and the pigments

which were mixed to make the colour.

Step 2 : An opaque object appears the colour of the light it reflects

The ruler reflects red light and absorbs all othercolours. There-

fore the ruler appears tobe red.

Step 3 : What pigments need tobe mixed to get red?

Red pigment is produced when magenta and yellow pigments

are mixed.

Example 10: Paint Colours

QUESTION

If cyan light shines ona dress that contains apigment that is capableof ab-

sorbing blue, what colour does the dress appear?

SOLUTION

Step 1 : Determine the component colours of cyan light

Cyan light is made up of blue and green light.

Step 2 : Determine solution

If the dress absorbs theblue light then the green light must be

reflected, so the dress will appear green!