Light The fact that light comes in many different wavelengths or frequencies
is the reason for many of the phenomena we see in nature. For example,
the sky at noon is blue - why not green or red or yellow? The sky
overhead is blue because air contains very tiny dust particles that are
even smaller than light waves. Of the many wavelengths of visible
light coming from the sun, blue light has the shorter wavelength.
Shorter wavelengths are much more likely to bump into the small particles
of dust than are the longer green and red wavelengths. And when
blue light
bumps into the dust, it scatters in all directions, some of it reaching
our eyes. The red and green light on the other hand do not so easily
scatter by the dust, so they continue straight on through, not scattering
to reach our eyes.
So why does the sun look red at sunset? You can answer this now
applying the same reasoning.
The finite size of the wavelength of light also becomes important
when you study things as
small as bacteria -- they are hardly bigger than the light waves, and
this means that our view of them must always be fuzzy.
In everyday life we deal mainly with objects that are
much larger than the wavelength of light, and then light
acts like a stream of tiny bullets that
travel in straight lines. In what follows we will
think of light this way.
About shadows