ScP033 Mixed Power Points

8/14/2019 ScP033 Mixed Power Points

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Light...

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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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with solutions.

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