1. Light

2. Light Fundamentals Light is a transverse wave
Light exhibits all of the wave behaviors: reflection, refraction, diffraction, etc.
Light does not require matter for a medium
Light can travel through a vacuum (no matter)
Can light travel through matter?

3. The electromagnetic spectrum includes
Visible light is a small range of wavelengths in the electromagnetic spectrum
Visible light is just the part of this spectrum we can see with our eyes
The electromagnetic spectrum includes
radio waves
microwaves
infrared
visible light
ultraviolet
X rays
Gamma rays

4. All electromagnetic (EM) waves travel at the same speed in a vacuum
This speed is called the speed of light and is represented by the small letter “c”
c = 3.00  108 m/s
c = f is the wave equation for all EM waves
Example: What is the frequency of yellow light,  = 556 nm?
Ans: f = c/ = (3.00  108 m/s)/(556  109 m)
= 5.40  /s
= 5.40  1014 Hz

5. The EM Spectrum

6. Light Behavior
When light strikes matter, three things can happen to the light energy
It is absorbed and becomes heat
It is transmitted (i.e., travels through the matter)
It is reflected
Reflection of Light
Light can be reflected in two different ways:
Regular reflection (a mirror)
Diffuse reflection (a white piece of paper)

7. The Law of Reflection:
The angle of reflection is equal to the angle of incidence, or r = i
reflected ray
incident ray
normal line
mirror i r

8. Using mirrors
Two examples:
2) A car headlight
1) A periscope

9. Color

10. Color What we see as color are different frequencies of visible light
The spectrum (or rainbow) is all of the colors in order of frequency (ROYGBIV)
Added together, the colors of the spectrum make white light
An object appears green because it reflects green light and absorbs the others

11. Additive Colors Our eyes have cone cells that detect three colors:
Red
Green
Blue
These are called the additive primary colors
The additive primary colors can be combined to form the other colors

13. Cyan, Yellow, and Magenta are often called the secondary colors
Two colors are complimentary when they add to make white
red + cyan = white
green + magenta = white
blue + yellow = white

14. Here is a glass prism:
A ray of white light arrives

15. What happens to the ray of light?
It is (mainly) reflected or refracted ?
But different colours are refracted by different angles.

16. cted refra In fact, the ray is : (bent through an angle), and
dispersed (split up into separate colours)
like this.

17. Red is deviated most / least ?
screen
Red is deviated most / least ?
Violet is deviated most / least ?

18. There is a spectrum on the screen:V
screen
There is a spectrum on the screen:
Red Orange Yellow Green Blue Indigo Violet
ROY G BIV

19. What is the real difference between red and violet light ?nm
wavelength
violet
red nm

20. Clear vs. Diffuse Reflection
Smooth, shiny surfaces have a clear reflection:
Rough, dull surfaces have a diffuse reflection.
Diffuse reflection is when light is scattered in different directions

21. Colour
White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow.
We can demonstrate this by splitting white light with a prism:
This is how rainbows are formed: sunlight is “split up” by raindrops.

22. Only red light is reflected
Seeing color
The apparent color of an object depends on the colors of light it reflects.
For example, a red book only reflects red light:
Homework
White
light
Only red light is reflected

23. A white hat would reflect all seven colours:
A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colours:
White
light

24. Using coloured light
If we look at a coloured object in coloured light we see something different. For example, consider a football kit:
Shirt looks red
White
light
Shorts look blue

25. In different colours of light this kit would look different:
Red
light
Shirt looks red
Shorts look black
Shirt looks black
Blue
light
Shorts look blue

26. Using filters Red Filter
Filters can be used to “block” out different colours of light:
Red Filter
Magenta Filter