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Q4. The human eye detects red light, blue light and green light. A combination of red, green and blue light is seen as white. We ‘see’ other colours when different combinations of red, blue and green enter the eye. This is shown in the table.
light entering
the eye |
|
colour ‘seen’ by the eye |
no light |
|
black |
red |
|
red |
blue |
|
blue |
green |
|
green |
red + blue |
|
magenta |
blue + green |
|
cyan |
red + green |
|
yellow |
red + blue + green |
|
white |
(a) Some magenta paint is illuminated by a combination of red, green and blue light.
Explain why the paint appears magenta.
2 marks
Magenta paint scatters blue and red light  but absorbs green light.
(b) A mixture of cyan paint and yellow paint appears green in a combination of
red + blue + green light. Explain what happens to:
(i) the red light?
1 mark
It is absorbed by the cyan paint but scattered by the yellow paint.
(ii) the blue light?
1 mark
It is scattered by the cyan paint but absorbed by the yellow paint.
(iii) the green light?
1 mark
It is scattered by the cyan and yellow paints. Therefore it is the dominant colour.
(c) Most colours of paint can be obtained by mixing different combinations of cyan, magenta and yellow paints.
What combination of these paints makes:
(i) blue paint?
Cyan and magenta
(ii) red paint?
Yellow and magenta
2 marks
Maximum 7 marks
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