Title: Properties of Light Part 1
1Properties of LightPart 1
2 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
6Reflection
- What does the term reflection mean?
- This occurs when a wave bounces off of a
material. - Light reflecting from an object is what makes it
visible
7Reflection
- When light hits a surface, some of it bounces off
or is reflected. Mirrors are very shiny surfaces
designed to reflect nearly all the light that
hits them.
8Reflection
- Reflection is most likely the property of light
that we experience most often. Looking at
yourself in a mirror, seeing the reflection of
the sun in the ocean at sunset, and the sight of
a mirage on the hot desert sand are all examples
of reflection. In fact, everything you can see is
the result of a complex pattern of light
reflecting off the surface of something.
9Shadows are places where light is blocked
10color
- 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 This is how rainbows are formed
sunlight is split up by raindrops.
11The colors of the rainbow
- Red
- Orange
- Yellow
- Green
- Blue
- Indigo
- Violet
12Seeing color
- The color an object appears depends on the colors
of light it reflects.
For example, a red book only reflects red light
White light
Only red light is reflected
13A 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 colors
White light
14Using colored light
- If we look at a colored object in colored light
we see something different. For example,
consider a football kit
Shirt looks red
White light
Shorts look blue
15Red light
Shirt looks red
- In different colors of light this kit would look
different
Shorts look black
Shirt looks black
Blue light
Shorts look blue
16Red
White
Blue
Green
Magenta
Yellow
Cyan
17How do we see color?
Color originates in light. Sunlight, as we
perceive it, is colorless. In reality, a rainbow
is testimony to the fact that all the colors of
the spectrum are present in white light. As
illustrated in the diagram below, light goes from
the source (the sun) to the object (the apple),
and finally to the detector (the eye and brain).
18Refraction
What does the term refraction mean? Refraction
occurs when the path of light wave changes as it
moves from one material to another.
19The picture of the ruler appears to be broken,
even thought it is not. It appears broken because
light travels through water and glass at
different speeds. The light waves refract or
bends as they pass from water to glass to air.
20Refraction In Our World
- How is refraction put to good use?
- Devices that refract light include eyeglasses,
contact lenses, cameras, microscopes, and
telescopes.
21Review Questions for Test
- Define the terms reflection and refraction.
- Briefly discuss how we see color.
- Name a tool that is used in our world to reflect
light.
22Review continued
- 4. Name a tool in our world that refracts light?
- 5. In the picture of the ruler, what makes the
ruler appear as if it is broken?