Light
Colour
How do we see colours?
White light, the light you see from globes, fluorescent tubes or the sun, is made up of lots of different colours.
White light
Red
Orange
Yellow
Green
Blue
Indigo
Violet
Rainbow
Red
Orange
Red Orange Yellow
Red Orange Yellow Green
Red Orange Yellow Green Blue
Red Orange Yellow Green Blue Indigo
Red Orange Yellow Green Blue Indigo Violet
We can separate the colours in white light in a controlled setting.
So what is happening?
Transparent (clear) prism
Ray of light
Refraction at surface due to difference in densities
Internal Reflection. Some of the light is internally reflected.
Refraction again as the density changes
Dispersion
Objects have different colours, how does this work?
Our eye
Object in the dark (Cannot be seen)
We can only see objects when light reflected or produced by them reaches our eyes
So how do objects appear to have different colours?
We know that white light is made up of different colours.
Replace this white light ray with the diffused colours
All colours are absorbed by the object, except red.
All colours are absorbed by the object except red. Red light is diffusely reflected. This is the red light we see, making the object appear red.
What happens when the light source is not white?
The Abyss (1989)
Blue wire with white stripe The Abyss (1989)
Blue wire with white stripe Black wire with yellow stripe
Blue wire with white stripe Black wire with yellow stripe Yellow light source
Blue wire with white stripe Black wire with yellow stripe Due to the yellow light source the wires appear the same colour.
So what is happening?
In the case of the Abyss movie,. the yellow light source means that yellow light is reflected from the yellow and white bands on the wires, making them both appear yellow. The black and blue bands do not reflect yellow light at all, so they both appear black.
Surface of a “red” object
Ray of white light.
Red wavelengths (colour) are diffusely reflected. All other wavelengths (colours) are absorbed.