The main point of this simulation is to show that light rays leaving an object travel in straight lines. The simulation has two light bulbs that can be turned on or off independently. The bulbs can be dragged around the screen to change their positions. The light from the bulbs either passes through a mask with a hole in it, or it is blocked by an object, as it travels to a screen on the right of the simulation. Investigate how the patterns of light and shadows change as you move the bulbs, the mask or object, and/or the screen, and as you change the size of the mask or object.

For Teachers

# Activities

1. Start with the mask and just one of the light sources. This illuminates part of the screen. Let's say you wanted to illuminate a larger part of the screen. Could you do this by moving the light source? If so, do you move the light source toward the screen or away from the screen? Could you, instead, illuminate more of the screen by moving the mask? If so, do you move the mask toward the source or away from the source? Could you, instead, illuminate more of the screen by moving the screen? If so, do you move the screen toward the mask and the source or away from the mask and source?
2. Before you turn on the second source, predict the color that will be produced in a region that is illuminated by both sources simultaneously. Turn on the second source (so both the red source and the blue source emit light), and check your prediction.
3. Using two sources and the mask, determine the conditions under which the sources light up distinct (non-overlapping) regions on the screen, and when they light up overlapping regions of the screen.
4. Now use just one source and an object, which casts a shadow on the screen. Let's say you wanted the shadow to cover a larger part of the screen. Could you do this by moving the light source? If so, do you move the light source toward the screen or away from the screen? Could you, instead, produce a larger shadow on the screen by moving the mask? If so, do you move the mask toward the source or away from the source? Could you, instead, produce a larger shadow on the screen by moving the screen? If so, do you move the screen toward the mask and the source or away from the mask and source?
5. How do your answers to activity 1 compare to your answers to activity 4? Explain what the connection is between the two activitoes.

### Translations

Code Language Translator Run
zh CN Chinese (CN ) 中文（CN ）

### Software Requirements

SoftwareRequirements

 Android iOS Windows MacOS with best with Chrome Chrome Chrome Chrome support full-screen? Yes. Chrome/Opera No. Firefox/ Samsung Internet Not yet Yes Yes cannot work on some mobile browser that don't understand JavaScript such as..... cannot work on Internet Explorer 9 and below

### Credits

Andrew Duffy; lookang (This email address is being protected from spambots. You need JavaScript enabled to view it.); Tina Tan

### Pre-requisites/ Prior Knowledge

Pupils should be able/already known how to:

• Define what is meant by a light source.
• Give examples of light sources in their everyday lives.

### Sample Learning Goals

At the end of the lesson, pupils will be able to:

• Determine how light travels.
• Draw the path of light from a light source to our eyes.

### For Teachers

1. Recognise that an object can be seen when it reflects light or when it is a source of light.

2. Recognise that a shadow is formed when light is completely or partially blocked by an object

### Hands-on

Teacher will guide the pupils through the next part of the experiment.

Each group will be given:-

1. a torchlight
2. blank white paper
3. measuring cylinder

Using the materials given and imagine that the torch is our primary light source, which is the Sun, investigate if the different position of the Sun in the sky at different times of the day have any effect on the shadow formed by an object.

What do you notice about the shadow as you move the torch following the path of the Sun?

Is the length of the shadow the same throughout the day?

### Connected to Real Life

1. Long shadows are cast in the morning and evening when the sun is low in the sky.

2. Shadows are shortest at noon when the sun is directly overhead.

3. Shadows always point in the opposite direction from the sun.

### Video

Science - Light and Shadow - Basic - English bBodhaguru

Gruppe Pilobolus Amazing Shadow Dance by

Guiding Questions:

Show YouTube videos on shadow puppetry. Begin by investigating and asking the following questions: What is a shadow puppet? How are they put together? How do they move?  Where have you seen shadows? Can you make shadows creatures with your own hands?

### Research

http://www.lajpe.org/dec15/08_1019_Bulbul.pdf
first study is published in LAJPE: http://www.lajpe.org/dec15/08_1019_Bulbul.pdf
Dr. M. Şahin BÜLBÜL
http://www.fizikli.com/editor

### Version:

1. http://weelookang.blogspot.sg/2013/08/light-and-shadow-model.html an initial draft simulation for research by This email address is being protected from spambots. You need JavaScript enabled to view it.
2. http://weelookang.blogspot.sg/2013/08/refraction-model.html an initial remix based on Andrew Duffy's work
3. http://www.compadre.org/osp/items/detail.cfm?ID=9983 an original simulation by Andrew Duffy
4. https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_light_and_shadowwee.jar my dropbox copy of simulation by Andrew duffy and lookang
5. http://iwant2study.org/lookangejss/04waves_13light/ejs/ejs_light_and_shadowwee.jar server copy of simulation by Andrew duffy and lookang