1. Primary Colours of Light
red, green and blue are the primary colours
when they combine they form other “secondary” colours

2. Colour white light is made up of all the other colours
we can use a prism to split a ray of white light up into bands of different colours

3. The Spectrum
when white light is refracted into different colours the resulting pattern is called a spectrum
ROY G. BIV
Red
Orange
Yellow
Green
Blue
Indigo
Violet

4. What is a rainbow?
water droplets in the air act like a bunch of prisms… when sun shines on them they refract the light… and form a spectrum

5. Why do we see a certain color?
white light (with all colors) strikes an object
if all colors are reflected we see WHITE
if no colors are reflected we see BLACK
if one color is reflected … we see that color
blue sky: particles of gas in the air are reflecting blue light
green grass: grass is reflecting green

6. How do we see color?
in the retina we have 2 kinds of cells that respond to light
rods detect the presence of light (and dark)
cones detect colour
there are 3 types… one for each primary colour
info from rods and cones go to the brain via the optic nerve
your brain interprets the colours from the messages it gets

7. Color Blindness
sometimes cone cells in people’s eyes are unable to detect certain colors
this is an inherited trait called color blindness
total color blindness: person does not see color
partial color blindness
people can’t distinguish between red & green
people can’t distinguish between blue & yellow
affects 8 – 12% males, less than 1% females
most common