1. Light and Sound In this unit: Properties of light Reflection Colours
Refraction
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. 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.

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

6. Luminous and non-luminous objects
A luminous object is one that produces light.
A non-luminous object is one that reflects light.
Luminous objects
Reflectors

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 Reflection from a mirror: 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. 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

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

13. Part 3 - 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.

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

15. 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

16. 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

17. 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

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

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

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

21. Red
Blue
Green
White
Yellow
Cyan
Magenta

22. Part 4 - Refraction
Refraction is when waves speed up or slow down due to travelling in a different medium. A medium is something that waves will travel through. When a pen is placed in water it looks broken.
In this case the light rays are slowed down by the water and are bent causing the pen to look odd. The two mediums in this example are water and air.

23. Part 5 – Sound We hear things when they vibrate.
If something vibrates with a high frequency (vibrates very quickly) we say it has a high pitch.
If something vibrates with a low frequency (vibrates slowly) we say it has a low pitch.

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

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

26. Part 6 - Hearing Our hearing range can be damaged by several things:
Too much ear wax!
Damage to the auditory nerve
Illness or infections
Old age (like Ms. Gerlach)

27. Other sound effects… Like light, sound can be…
Reflected – sound reflections are called echoes.
Refracted – this is why you might sound strange if you try talking underwater.

28. The Ear Look at the diagram using the following descriptions:
A -This part “channels” the sound towards the ear drum.
B - This tube carries the sound towards the eardrum.
C - This part “picks up” the vibrations.
D -These bones are vibrated by the eardrum .
E - This part is used to help us keep our balance.
F -This part of the ear contains small hairs with turn vibrations into an electrical signal.
G - This part connects the ear to the mouth.
The Ear