Schadow

• Natuurkunde
• Middelbare school
• havo, vwo
• Leerjaar 2,3

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You can explain the difference between point sources and big lightsources

You can explain what causes half and full shadows

You are familliar with the concepts of divergent, convergent and parallal lightbeams

You can explain lunar and solar eclips 

You can replicate lunar and solar eclipses using a drawing

You can explain the different phases of the moon

You can explain why we have different seasons 

You can explain the difference in lightintensity during different seasons

Schadow

In the early days when there were no computers, smartphones or other high-tec gadgets, people did find a way to enjoy themselves using light and shadow. Oldfashioned and boring? Perhaps, but we make use of it even now and people are still enjoying the playfull way we use light and shadow together.

Schadow

"Schaduw comes to life if the light of a lightsource is wholy or partially blocked by an object. A precondition for having shadows is that you need a lightsource and a blocking object.

Furthermore, you can differentiate in the kind of lightsources which can be divided into natural lightsources (like the sun) and artificial lightsources (like a man made lamp).

wikipedia

poem

Light and shadow

You need light to see shadows

Light rays travel in straight lines

Schadows exist in places 

were light is blocked

Different kind of lightbeams

Divergent lightbeam: 
Lightrays move away from each other

They seem to orginate from one point  

                     

Parallel lightbeams:  
Lichtrays stay at equal distance

Convergent lichtbeam: 

Lightrays are focussed on one point

Pointsource or Large lightsource

pointsource

_{A pointsource is a lightsource for which assume that all light originates from a very small point. In reality this often is not the case since most lightsources are most of the time bigger than a small point of light.}

big lightsource

_{If the lightsource is very big, the object will receive light from multiple angles which results in different shadows.}

Different kinds of shadows

• Half shadow (penumbra): 
  A shadow which still receives partial light of the lightsource

• Full schadow (umbra):
  A shadow which receives no light at all
  
• Workingspaces are better for working if you do not have a lot of sharp shadows. Therefore we make use of large fluorescent tubes.
  

Peculiar schadows

Where are the lightsources?

A stadium needs a lot of light to make all shadows dissapear

Nice how a shadow give you another look at things

Would this be during the day or at night?

Why do you think so?

This is how red, green and blue mix

Click on the picture for an overview

Colored light sources will provide nice shadows

Blue sky

Sun& solar eclipses

Why is the sky blue?

Watch the video and make a note

about why the sky is blue

The moon will be in different phases during a month. This has to do with the orbit of the moon around the earth and how the moon is situated to both the earth and the sun.

Corona

another word for the circel around the sun during a solar eclips

but now famous 

for something 

completely 

different

explanation

The sun is very big in relation to the earth.

Therefore you do not draw it like a point source.

And if you do not have a point source you will get full and half shadows.

explanation

This picture makes clear that when the sun is shining at an angle (which especially is the case during winter time), the liughtintensity is far less because the same amount of light is spread over a larger distance.

Seasons

The axis of the earth is always at an angle relative to the sun.

Because of this summer and winter will take turns with each other on the northern and southern halves of the earth.

A couple of colors is prjected onto a screen.

Drag the colors to the right spot

Black

Green

Yellow

White

Magenta

Blue

White

Who is nearest to the screen?

1. The girl
2. The mother

Where do you find a halfshadow?

A

B

C

1. A
2. B
3. C

Explain to me why the color of the sky is blue?

Why can we see light?

1. reflection
2. diffusion
3. parallel
4. dispersion

At the spot where you see a halfshadow,
there is no light

1. True
2. Not true

You cannot see light rays

1. True
2. Not true

The shadow of an object is bigger than the object itself with a divergent lightbeam.

1. True
2. Not true

SIMULATION

Light is moving in straight lines does it not?

Keep in mind that light has wave like properties. Because of this, light can bend around a corner when it goes through a very narrow opening. You do not have to remember this, this is more something for higher education. But it is nice to know that strange things can happen.