ScP033 Mixed Power Points
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Transcript of ScP033 Mixed Power Points
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Light...
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ScP033 Mixed PowerPoints
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Consider the picture below..
Why can the Belinda see the cat, but not the dog?
Belinda
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This is also the reason
why shadows occur
when something gets in
the way of the light.
Light travels in
straight lines
Lets start at the beginning.
This is why we cannot
see around corners.
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For you to be able to see an object, light must
travel from the object to your eye.
The light that hits the object usually comes from
somewhere else
maybe the Sun
or perhaps from a light bulb, candle or torch.
These are called light sources.
How do we see things?
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It must then be ref lected off the object andtravel to your eyes.
How do we see things?
So, in order to see an object, light must travelfrom the source to the object
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Belinda can see the
cat.
This is because
light from thesource can reach
the cat ...
and the reflected
light from the cat
can travel in a
straight line to
Belindas eyes.
So, looking at that picture again...
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Belinda cant seethe dog.Even though light
from the source canreach the dog ...
the reflected light
from the dog cannot
travel straight toBelindas eyes.
So, looking at that picture again...
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Can the girl see the person in the mask?On your worksheet, draw light rays in order to
determine whether she can or not.
NoAnd the answer
Consider the picture below..
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Light travels in lines that are
straight.
Some things, such as the Sun and light bulbs
give out their own light. These are called
light sources.
Other examples of light sources are
candles and torches.
Summary so far
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reflect the light that has come
from a source.
For you to see the object, this
reflected light must be able to
travel in a straight line to your
eyes.
Summary so far
Most things dont give out their
own light. They simply
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A very smooth surface, such as a
mirror or a still pond, will reflect a
beam of light in one directiononly.
Mirror
These thin
beams of light
are called
light rays.
Reflection from Smooth Surfaces
This type of object is said to have a
glossy (or shiny) surface.
A clear reflection is seen in thesurface.
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Most objects are not smooth,especially when viewed under a
microscope.
In these cases, the light is
reflected in all directions.
Reflection from Rough Surfaces
A clear reflection is not seen in theobject.
Surface of
Paper
(under a
microscope)
This type of object is said to have a
Matt surface.
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at exactly the same
angle.
Mirror
700
700
Which brings us to the Law of Reflection
If a ray of light is
directed at a mirror
at a certain angle
it will be reflected
from the mirror
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Or, in more theoretical
terms:
Which brings us to the Law of Reflection
200
200angle ofreflection, r
angle of
incidence, i
Normal
angle of incidence
angle i =angle r
=angle of reflection
Mirror
700
700
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Show on your diagram what happens to the ray
of light next.
400 400
Drawing Rays
Press the Spacebar when you have finished.
mirror
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and this ray of light?
300 300
Drawing Rays
Press the Spacebar when you have finished.
mirror
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The law of reflection has been known for some
time.
In fact, the pyramids in Egypt were decorated bypeople who understood it.
The artists working in the Pharaohs tomb needed
to have enough light to see their painting.
The Pyramids
They didnt use oil lamps or
candles, because that would
have left marks on the walls
from the dark smoke.
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So that light
could be
reflected into
each chamber,
polished metalmirrors were
placed along the
corridors!
The Pyramids
The light could
then reflect all
the way to the
artist in the
tomb.
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The amount of light reaching the burial
chamber would have been very small.
The artists eyes, however, would have slowly
adjusted to the small amount of light.
The Pyramids
When the artist left the tomb,
the daylight would have
seemed blindingly bright.
Unfortunately, each time light is reflected,
some of it is absorbed. The light intensity
would drop with each reflection.
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In this way, the artists life was
dedicated to the Pharaoh.
The Pyramids
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Claire is performing a light experiment.Using a ray box, she sends a ray of light towards
a mirror.
Light Experiments
She can also trace the reflected ray.
She places a piece of paper underneath the ray
box and mirror, so that she can mark in the
direction of the ray before it strikes the mirror.
100ray box
100
mirror
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Using this information, fill in the table on your
worksheet.
b. 200
c. 300
d. 450
e. 600
Light Experiments
Claire carries out the experiment five times,using different angles each time.
These are the angles she directed the ray from:
a. 100
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Which angle must Claire have recorded
incorrectly?
Answer: 450
/ 550
Angle that light strikes the
mirror
Angle that light reflects
from the mirror
100
200
300 300
450
600
100
200
550
600
This is the table that Claire completed aftermeasuring each of the angles.
Light Experiments
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ORB Education
Visit http://www.orbedu.com for the full, editable versions
with solutions.
ScP033 Mixed PowerPoints
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