Optics
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Propagation of light
Speed of light
At human scale, light seems to propagate instantly from one point to another nevertheless the speed of light is not infinite.
This speed is really huge for our human senses and scientifics had been unable to measure it for a long time.
In emptiness the speed of light has the following approximate value:
300 000 km/s
or 300 000 000 m/s
or 3 x 108 m/s
This speed has roughly the same value in the air but is lower in water ( 225 000 km/s ) and in glass ( 200 000 km/s ).
More generally speed of light is lower in transparent mediums than in emptiness or air.
| 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 |
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