Physics - Ideas about light and matter
Ideas about light and matter
Humans have been trying to understand the nature of light for a long time.
This area of study looks at the development of ideas in the last four
centuries. During this time the two main models used to describe light have
been the _particle model,_ as proposed by Newton, and the _wave model,_ as
proposed by _Huygens._ Each theory has been favoured at different times as
a result of the scientific evidence available at the time.
This section will look at some of the properties of light and consider how
well the particle and wave models explain these properties.
The particle model says that light is a stream of fast moving particles.
The particles move in straight lines with constant velocity  through a
uniform medium. The straight paths can be used to explain the sharpness of
The wave model says that light is a periodic disturbance of a medium. It
would therefore be similar to sound waves and water waves. An immediate
difficulty for a wave theory is to explain what the medium for light is in
a vacuum. Waves also travel in straight lines, in a uniform medium, from a
source to a distant location and they also maintain a constant speed in a
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