1. 4.2: Properties of Visible Light
Chapter 4
4.2: Properties of Visible Light

2. Wave Model of Light How does light travel?
Light travels through empty space as a wave
Basically light is a wave that you can see!
Light transfers ENERGY from one place to another
Ex: Light travels from the Sun to Earth
This explanation is called the ‘Wave Model of Light’

4. Refraction of Light
When light is travels through air at a certain speed and then enters another material (ex: water) where it will travel at a different speed…
the wave of light will be bent or refracted

5. Refraction of Light
Refraction is the bending or changing direction of a wave as it passes through one material to another.

7. Refraction of Light
Why does light shone through a prism produce a rainbow of colours?
White light (sunlight) is made of waves that have different wavelengths and frequencies
When this light passes through a prism, the waves are refracted
But the waves bend by different amounts since they have different wavelengths
Different colours are separated when they come out the other side of the prism!

8. Colours of the Rainbow Just like a prism, water also refracts light
After a rainfall, the water droplets in the mist refract light
The result is a rainbow…the spectrum of colours that make up visible light

9. Colours of the Rainbow
Visible light is made up of waves that we see as colours when separated by refraction
Each colour or wave has a different wavelength and frequency
This range of colours of visible light is called the visible spectrum.

10. Frequency vs. Wavelength
Here is a simulator to demonstrate the different wavelengths of light.

11. The 7 colours of visible light
There are seven colours that are most easily seen in a rainbow.
In order from long to short wavelength (low to high frequency), they are:
Red – Orange – Yellow – Green – Blue- Indigo – Violet
***You can remember the order by this trick:
They spell the name ROY G BIV

12. Colour and Reflection Some materials refract light (bend it)
When light hits some materials and objects, the light bounces off.
This is called REFLECTION of light

13. Reflection & Colour – the Connection!
Remember, light is made up of waves of different colours
Some objects absorb some of these colours and reflect the remaining colours.
Only the reflected colours can be seen (that means a green leaf is actually absorbing all the colours except green!)

15. The Additive Primary Colours
Only three colours are actually needed to produce all the colours of a rainbow…
These colours are often called the additive primary colours:
RED, BLUE AND GREEN
Adding all 3 colours in the right amounts will make white light

16. Secondary Colours
The light of 2 primary additive colours makes a secondary colour
Green + blue = cyan
Green + red = yellow
Red + blue = magenta
YELLOW