|Why do different colors of light have different
|Question Date: 2016-11-15|
We have chemicals in our eyes that are able to
see light of certain energy levels. When one
of these chemicals sees light of that level, the
cells containing that chemical tells the rest of
our brains that we've seen that light. Our brains
then tell us that we've seen the color of light
that has that energy level. It all happens
because of the way that our brains are wired -
light has color because of what our brains see,
not because of the energy of light itself. We
have chemicals to see the colors of light that we
do because those are the energy levels that the
sun emits the most of. Had we evolved on a planet
orbiting another star, we would see colors of
light that match the light coming out of that
It is probably easiest in this case to think of
light like a wave. Different colors of light
correspond to waves with different
frequencies. This is to say that different
colors of light are just waves that oscillate
(that is, swing back and forth) a certain number
of times per second. For orange light, the wave
oscillates 500 000 000 000 000 times per second.
Blue light waves oscillate more quickly (higher
energy), and red light waves oscillate more slowly
To think of why higher frequency waves (or
waves that oscillate more quickly) have higher
energy, imagine you have a rope and you're trying
to swing it back and forth. It's easier to swing
the rope back and forth slowly, and the faster you
want to swing it, the more energy it takes.
Light travels as a wave packet, and packets of
light always travels at the same speed in one
given material. For example, red light packets and
blue light packets have the same speed in air.
The difference in energy between red and blue
light has to do with wavelength inside of
the packet. Wavelength is the distance between
two peaks of a wave (see below). Red light has
longer wavelength, and blue light has shorter
wavelength. In other words, blue light has more
energy, so it oscillates more within the packet
than red light does.
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