Visible Light

Visible light is the light that our eyes can detect.

Light is…

A type of energy

Other types of energy are:

Heat, electricity, sound, chemical and …

Notes

Light is not …

The sunA globeA flourescent light

These are sources of light!!

Notes

Light is not ..

… necessarily made up of rays

This is just the model for light that we use to help us to predict what will happen is certain situations

Notes

Luminous Objects …

…produce light which allows us to see them. They are also called sources of light and can be categorised as:

Notes

•Incandescent sources•Fluorescent sources•Chemoluminescent sources•Bioluminescent sources

Incandescent sources…

...produce light from fast moving electrons that result from the heating a metal or gas

e.g.candles, light bulbs,

and the sun

Notes

Fluorescent sources…

…. fire electrons into gases causing the electrons in the gas atoms to jump to higher shells. When the electrons return to their normal shell they give off light.

Notes

Chemoluminescence

A form of energy

Notes

Chemoluminescence

A form of energy

Notes

Bioluminescence Notes

What’s Your Theory?

If non Luminous objects don’t produce their own light, why can we see them at all angles irrespective of where the source is?

Notes

What the scientists say.

Virtually all objects have a rough surface when you look at them through a strong microscope. These rough surfaces reflect light at all angles.

We call this type of reflection Diffuse Reflection

Notes

What’s Your Theory?

Why do different objects appear to be different colours?

Notes

What the scientists say.

Light rays can have different energies and our eyes can detect the rays that have energies in the visible spectrum range.

Notes

Note !! infrared is shown as black

High EndLow End

White is not in the spectrum!

There is no such thing as white light.

White light is a result of all the colours of the rainbow being put together.

Light globes, fluorescent lights and the sun all appear to give us white light which actually means that they are producing all the colours of the rainbow mixed together.

Notes

Proof 1: PrismNotes

Proof 2: RainbowNotes

Proof 3: Newton’s Colour WheelNotes

Why do objects appear coloured? Coloured objects are usually non luminous so

they do not give off coloured light. Instead they absorb some colours and reflect

others. So a red object reflects red and absorbs the

other colours. Filters do the same thing e.g. a green filter

absorbs all the colours except green.

Notes

Colour Subtraction

http://mysite.verizon.net/vzeoacw1/colorsub.html

Notes

Cyan, Yellow and Magenta are known as the

Artists Primary Colours

What’s Your Theory?

How do the old TV screens give us coloured pictures?

Notes

What the technicians say.

Notes

What the technicians say.

Notes

Colour Addition

http://mysite.verizon.net/vzeoacw1/coloradd.html

Notes

Green, Blue and Red are known as the

Scientists Primary Colours

Comparing The Two SystemsNotes

What’s Your Theory?

Why do we see rainbows?

Where do we see rainbows?

Notes

What the scientists say.Notes

Where do we see rainbows?Notes