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Free online optic lesson
for elementary school, middle school and high school.
Rectilinear propagation of light
What is propagation of light ?
isn't made of matter ( we can't touch it ! ) it would be unsuitable to
say light moves: in order to describe its travel through
space we can say it " propagates ".
We can also use the term " propagation " for sounds and waves because
there's no motion of matter in these cases.
light can propagate only in transparent mediums like air, glass or
In this kind of medium, light has a rectilinear propagation: it means
that light propagates in straight line.
Furthermore, this rectilinear propagation requires an homogenous medium
that has same physical properties ( temperature, density, pressure etc
) and chemical properties ( composition ) at each of its points.
What is a ray of light ?
The path of
light can be represented drawing a ray of light.
As for light has a rectilinear propagation, a ray of light can be drawn
as a line with an arrow that shows direction of propagation.
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