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 kilometers 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. Energy in Light
-There is a lot of energy in light. -For example, when you stand in the sun you feel the sun’s energy through heat. -If you absorb too much of that energy, you can get a sunburn. -A lamp doesn’t have as much energy as the sun- you can’t get sunburned by a lamp. -However, a lamp does give off heat because of the electric current it takes to make it work.

9. 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.
Light gives off energy in the form of heat.

10. Part 2: Reflection
-When light hits an object, the object affects the path of the light. -An object can absorb light, make it bounce off, or let it pass through. -Some light energy is absorbed. Darker objects absorb more light energy-that’s why you are hotter when you wear dark colors on a hot day. -Objects don’t absorb all the light that hits them. Some of the light bounces off. Reflection is the bouncing of light from a surface.

11. Part 2:Reflection
-Usually, light scatters in many directions when it is reflected. -A smooth surface reflects light in a clear and predictable pattern. -Have you ever seen a reflection in clear windows on a building? -Looking in a mirror can also get you a smooth reflection, but it gives you a backward image.

12. Reflection from a mirror:
Normal
Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Mirror

13. 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 !!!

14. Refraction
When light moves from water to air, its speed changes. The change in speed makes the beam of light bend. This bending of light is called refraction. Refraction is bending light.
When a pen is placed in water it looks like this:
Refracted light can make a solid object look like it is broken into two parts. It looks like that because the light from the part of the pencil that is under the water reaches your eyes on a different path.

15. Translucent Materials
-Materials that let some light through are called translucent. An example of a translucent material is a frosted light bulb.

16. Transparent Materials
-A transparent material allows most of the light that hits it to pass through it.
-Most glass, water, and some plastics are transparent.
-Transparent objects don’t scatter light, but they do refract it.

17. Opaque Materials
-Materials that do not allow any light to pass through them are opaque.
-Opaque materials absorb all the light into them.
-Metal, wood, and most of your body is opaque.

18. Color
White light is not a single color; it is made up of a mixture of the seven colors of the rainbow.
We can demonstrate this by splitting white light with a prism:

19. Light and Color
-As light enters a prism, the light waves change directions and separate (this is an example of refraction).
-You are able to see all the colors of the rainbow when the colors separate.
-You can remember all the colors of the rainbow with ROYGBIV.
-When have you seen a rainbow of color?

20. The colors of the rainbow:
Red
Orange
Yellow
Green
Blue
Indigo
Violet

21. Lenses -A lens is a curved, transparent object that refracts light.
-There are different types of lenses with different types of curves.

22. Convex Lens -A convex lens is thicker in the middle than at the edges.
-As light waves move through the lens, they bend towards the thickest part-the middle.
-A convex lens makes light waves come together and make objects appear larger or magnified.

23. Concave Lens
-A concave lens is thicker at the edges than in the middle.
-As light waves enter the lens, they bend toward the thicker part- the ends.
-The concave lens makes light waves spread out and this makes objects appear smaller.

24. 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

25. 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

26. 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

27. 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

28. 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

29. Some further examples:
Object
Colour of light
Colour object seems to be
Red socks
Red
Blue
Black
Green
Blue teddy
Green camel
Magenta book
Homework

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

31. Investigating filters
Colour of filter
Colours that could be “seen”
Red
Green
Blue
Cyan
Magenta
Yellow

32. Red
Blue
Green
White
Yellow
Cyan
Magenta

33. 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.
The lowest frequency I could hear was…
Words – slowly, low, high, quickly

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

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

36. 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)

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

38. The Ear Label your diagram with the following:
These bones are vibrated by the eardrum
This tube carries the sound towards the eardrum
This part is used to help us keep our balance
This part “picks up” the vibrations
This part of the ear contains many small hairs with turn vibrations into an electrical signal
This part connects the ear to the mouth
This part “channels” the sound towards the ear drum

39. The Ear