1. Light and Sound Properties of light Reflection Colours Refraction
Properties of light
Reflection
Colours
Refraction
Diffraction
Properties of sound
Hearing

2. Part 1 – Properties of Light
Light travels in straight lines:
Laser

3. Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.

4. electromagnetic spectrum

5. Light travels much faster than sound. For example:
Thunder and lightning start at the same time, but we will see the lightning first.
2) When a starting pistol is fired we see the smoke first and then hear the bang.

6. We see things because they reflect light into our eyes:
Homework

7. Shadows
Shadows are places where light is “blocked”:
Rays of light

8. Properties of Light summary
Light travels in straight lines
Light travels much faster than sound
We see things because they reflect light into our eyes
Shadows are formed when light is blocked by an object

9. Part 2 - Reflection When a wave balance off an object at a angle
Like a reflection from a mirror:
Normal
Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Mirror

10. Angle of incidence = Angle of reflection
The Law of Reflection
Angle of incidence = Angle of reflection
In other words, light gets reflected from a surface at ____ _____ angle it hits it.
The same !!!

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

12. Diffraction of Waves
Diffraction involves a change in direction of waves as they pass through an opening or around a barrier in their path.
Water waves and sound have the ability to travel around corners, around obstacles and through openings.

13. The colours of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet

14. Adding colours
White light can be split up to make separate colours. These colours can be added together again.
The primary colours of light are red, blue and green:
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan (light blue)
Adding red and green makes yellow
Adding all three makes white again

15. Only red light is reflected
Seeing colour
The colour an object appears depends on the colours of light it reflects.
For example, a red book only reflects red light:
Homework
White
light
Only red light is reflected

16. 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

17. 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

18. 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

19. Red
Blue
Green
White
Yellow
Cyan
Magenta

20. Words – speed up, water, air, bent
Refraction
Reflection involves a change in direction of waves when they bounce off a barrier
A medium is something that waves will travel through. When a pen is placed in water it looks like this:
In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______.
Words – speed up, water, air, bent

23. Words – slowly, low, high, quickly
Sound – The basics
We hear things when they vibrate.
If something vibrates with a high frequency (vibrates very ______) we say it has a _____ pitch.
If something vibrates with a low frequency (vibrates ______) we say it has a ____ pitch.
Words – slowly, low, high, quickly

24. Drawing sounds… This sound wave has a _____ frequency:

25. Drawing sounds… This sound wave has a _____ amplitude (loud):
This sound wave has a _____ amplitude (quiet):

26. Hearing problems Our hearing range can be damaged by several things:
Too much ear wax!
Damage to the auditory nerve
Illness or infections
Old age (not like Mr Richards)