Colored light

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Colored lights

1) Filters and colored lights

A filter consists of a colored transparent material: light can pass through it, but its color is modified.
A red filter allows to get red light, a blue filter allows to get blue light etc.
More generally, a filter allows to obtain a light whose colore is the same as it.

White light is a mix of colored lights and a filter can only be crossed by one of them. The other colored lights are stopped. For instance, a red filter can be crossed by a red light but blue and yellow lights are stopped.

2) Primary colors

Some new colored lights can be obtained mixing several colored lights: this is the additive color synthesis.
Nevertheless there are three colors that allow to obtain all other colors.
These colors are red, green and blue: they are called primary colors.
If mixing two beams of colored lights that have the same intensities, then you can get the following colors:
- Green and blue give cyan
- Blue and red give magenta
- Green and red give yellow
If these three primary colors are mixed together they form a white light.

This additive synthesis must be distinguished from the soustractive synthesis of colors, that consists of mixing colored materials like paints made of colored pigments that absorb light.

Science class

Optics lessons

Light sources

- Types of light sources
- Why can we see objects ?

Propagation of light

- Rectilinear propagation of light
- Beams of light
- Speed of light
- Light and distances

Shadows, lunar eclipses and phases of the moon

- Formation of shadows
- The Moon and eclipses

Colored lights - color of objects

- Decomposition of white light
- Colored lights
- Color of objects

Image formation - Thin lenses

- Thin converging and diverging lenses
- Image formation by thin lenses
- Vision and eyes