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Light Waves Notes

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Light Waves Notes Part 1 Properties of Light Light travels in straight lines: Laser Light travels VERY FAST around 300,000 kilometres per second. – PowerPoint PPT presentation

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Title: Light Waves Notes


1
Light Waves Notes
2
Part 1 Properties of Light
  • Light travels in straight lines

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
Sun Stars Light Bulb (when on) Firefly
Mirror Moon Person Desk Paper
7
Part 2 - Reflection
  • Reflection from a mirror

Normal
Reflected ray
Incident ray
Angle of reflection
Angle of incidence
Mirror
8
  • 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
The same !!!
9
Clear vs. Diffuse Reflection
  • Smooth, shiny surfaces have a _____ reflection

Clear
Rough, dull surfaces have a ______
reflection. Diffuse reflection is when light is
scattered in different directions
Diffuse
10
Using mirrors
  • Two examples

2) A car headlight
1) A periscope
11
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.
12
The colours of the rainbow
  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet

13
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 all three makes white again
Adding red and green makes yellow
14
Seeing colour
  • 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
15
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
16
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
17
  • 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
18
Some further examples
Object Colour of light Colour object seems to be
Red socks Red Red
Red socks Blue Black
Red socks Green Black
Blue teddy Red Black
Blue teddy Blue
Blue teddy Green
Green camel Red
Green camel Blue
Green camel Green
Magenta book Red
Magenta book Blue
Magenta book Green
blue
black
black
black
green
red
blue
black
19
Light Colour Bill Nye
  • http//www.youtube.com/watch?vgtgBHsSzCPE

20
Using filters
  • Filters can be used to block out different
    colours of light

21
Investigating filters
Colour of filter Colours that could be seen
Red
Green
Blue
Cyan
Magenta
Yellow
red
green
blue
Blue, green, cyan
Red, blue, magenta
Red, green, yellow
22
Red
White
Blue
Green
(All colors)
Primary Colours of Light
Black
Magenta
Yellow
Cyan
(No Color)
Secondary Colours of Light
23
Refraction
Speed up
Refraction is when waves _______ or slow down due
to travelling in a different _________. A medium
is the area or space that waves will travel
through. For example, if you put a pen in a
cup of water, the light rays are slowed down by
the water and are _____, causing the pen to look
odd. Two examples on next slide
medium
bent
24
?Due to change in medium, the phase velocity of
the wave is changed but its frequency remains
constant (the same).
25
Sound The basics
vibrate
We hear things when they ________. If something
vibrates with a ____________ (vibrates very
______) we say it has a _____ pitch. If something
vibrates with a ___________ (vibrates ______) we
say it has a ____ pitch.
High frequency
fast
high
Low frequency
low
slow
26
Drawing sounds
This sound wave has a _____ frequency
high
High pitch
This sound wave has a ___ _frequency
low
Low pitch
27
Drawing sounds
This sound wave has a _____ amplitude
high
Loud
This sound wave has a _____ amplitude
low
Quiet
28
?Conclusion
  • The pitch or note of a sound that we hear is
    determined by its wavelength or its frequency.
  • The shorter the wavelength, the higher the
    frequency becomes, and the higher the pitch that
    we hear.
  • The amplitude of a sound wave is the same thing
    as loudness.
  • The wavelength of a wave is independent of its
    amplitude loudness and inversely proportional
    to its frequency.

Independent wavelength does not affect
loudness. Inversely proportionalhigh frequency
short wavelength, low frequency
long wavelength
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