light

2. LLiigghhtt aanndd SSoouunndd
In this unit:
1) Properties of light
2) Reflection
3) Colours
4) Refraction
5) Properties of sound
6) Hearing

3. PPaarrtt 11 –– PPrrooppeerrttiieess ooff LLiigghhtt
Light travels in straight lines:
Laser

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

5. Light travels much faster than sound. For example:
1) 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. 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

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

9. PPrrooppeerrttiieess ooff LLiigghhtt ssuummmmaarryy
1) Light travels in straight lines
2) Light travels much faster than sound
3) We see things because they reflect light
into our eyes
4) Shadows are formed when light is blocked
by an object

10. PPaarrtt 22 -- RReefflleeccttiioonn
Reflection from a mirror:
Incident ray
Normal
Reflected ray
Angle of
incidence
Angle of
reflection
Mirror

11. TThhee LLaaww ooff RReefflleeccttiioonn
AAnnggllee ooff iinncciiddeennccee == AAnnggllee ooff rreefflleeccttiioonn
In other words, light gets reflected from a surface at
____ _____ angle it hits it.
The
same !!!

12. CClleeaarr vvss.. DDiiffffuussee RReefflleeccttiioonn
Smooth, shiny surfaces
have a clear reflection:
Rough, dull surfaces have
a diffuse reflection.
Diffuse reflection is when
light is scattered in
different directions

13. UUssiinngg mmiirrrroorrss
Two examples:
1) A periscope
2) A car headlight

14. CCoolloouurr
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.

15. TThhee ccoolloouurrss ooff tthhee rraaiinnbbooww::
Red
Orange
Yellow
Green
Blue
Indigo
Violet

16. AAddddiinngg ccoolloouurrss
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 all
three makes
white again
Adding red
and green
makes yellow

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

18. 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

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

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

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

22. UUssiinngg ffiilltteerrss
Filters can be used to “block” out different colours of light:
Red
Filter
Magenta
Filter

23. IInnvveessttiiggaattiinngg ffiilltteerrss
Colour of filter Colours that could be “seen”
Red
Green
Blue
Cyan
Magenta
Yellow

24. Red
Magenta
White
Yellow
Blue Green
Cyan

25. RReeffrraaccttiioonn
Refraction is when waves ____ __ or slow down due to
travelling in a different _________. 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

28. SSoouunndd –– TThhee bbaassiiccss
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

29. DDrraawwiinngg ssoouunnddss……
This sound wave has a
_____ frequency:
This sound wave has a
___ _frequency:

30. DDrraawwiinngg ssoouunnddss……
This sound wave has a
_____ amplitude
(loud):
This sound wave has a
_____ amplitude
(quiet):

31. HHeeaarriinngg pprroobblleemmss
Our hearing range can be damaged by several
things:
1) Too much ear wax!
2) Damage to the auditory nerve
3) Illness or infections
4) Old age (not like Mr Richards)

32. OOtthheerr ssoouunndd eeffffeeccttss……
Like light, sound can be…
1) Reflected – sound reflections are called
______.
2) Refracted – this is why you might sound
strange if you try talking underwater

33. TThhee EEaarr
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

34. TThhee EEaarr