Speed
Light travels at the speed of
1.03 X 10 8 . Amazing ? If you think a marathon champion runs fast. Think again. Compare
that and you will his speed at snail's pace. However, at this speed the sun still takes 8
minutes to reach us due to its extremely long distance.
Medium
For many things to travel
across to something else, a medium is needed. However in this case, light does not need a
medium to travel. Since it is a form of electromagnetic waves, it can just travel
normally in the absence of a medium. It can travel through a vacuum of space at the speed
of 186,282 miles per second. Thus, when compared with the speed of sound which is a mere
0.3 km per second, making the speed of sound too slow for words.
Propagation of Light
The sun radiates light and
heat energy. The light energy are transported in the form of rays. People usually get the
impression that we can 'see' rays. This phenomenon is caused by the scattering of light by
the suspended dust particles or water droplets. Scientists actually invented the idea of
rays. Thus, a ray of line is actually referring to the line along which the light travels.
On ray diagrams, they are actually represented by lines with arrows. In reality, they have
no arrows but they are used to indicate the direction of the ight rays. A bundle
of rays is known as a beam of light. The figure below shows you the 3 types of light
beams.
So much for theory, now let's
do the following experiment for you to see on your own that light really travels in
straight lines.
Observations
We can observe that it is only
that when the light bulb, the holes and eye is in one straight line will then the light
from the light bulb be seen. In other words, any thing that is displaced, no light can be
seen at the other end.
This shows that light
travels in a straight line , also known as the rectilinear propagation of light.
