Page 17 - Veterinary Laser Therapy in Small Animal Practice

CHAPTER 1

Light is just the catalyst

“Goodbye,” said the fox. “And now here is my secret, a 1.1 Electromagnetic radiation
very simple secret: It is only with the heart that one can
see rightly; what is essential is invisible to the eye.” Light has some very cool properties, both classical and
— Antoine de Saint-Exupéry quantum-mechanical (in fact, both at the same time),
and can be described in a bunch of different ways. But
After reading that last section you should feel like before you get scared off by the scary “quantum” word,
Harry Potter with the Elder Wand in your hand as let’s simplify this pragmatically. Light is simply an oscil-
you wield your laser. It is a powerful tool. But now lating electric and magnetic field. We call the distance
it’s time to burst your bubble and tell you that light between any two peaks of this oscillation the wave-
doesn’t do ANY of that. If you shine light on a vial length of light. One important, but somewhat obvious
of growth factors, you will get a slightly warmer vial feature of light is that it always travels at the same speed
of growth factors, nothing more. The body can, how- (in a vacuum; we’ll get to what happens in a medium
ever, be triggered to synthesize more of them. In later). That said, another equivalent way to define light
fact, all of the effects we just highlighted are simply is by the frequency, i.e. the number of oscillation cycles
enhancements of the body’s ability to regulate itself in per unit of time. (NOTE: This is not to be confused
a positive direction. And light can be that catalyst in a with pulse frequency or repetition rate. That has to
completely non-invasive way. In order to do so, it has do with turning light on and off periodically. We’ll get
to be absorbed, and by something that is somewhere to that later.) Since we know the wave’s propagation
early in the chain of interactions that causes the body speed (distance traveled per unit of time), if we know
to release those growth factors. The really cool part how many times it oscillates, we also know the distance
is that the body is so good at communication within between oscillations, and vice versa (Fig. 1.1).
itself that the initial trigger of these eventual events The ONLY fundamental difference between the dif-
can be seemingly unrelated to the desired effect. More ferent flavors of light is this one-dimensional scale of
on that later, but first, what does it even mean for the oscillating wave, whether you are referring to it
something to absorb light? as wavelength or frequency. In fact, depending on the
When you spill water on the table, you use a paper region of the full spectrum of light (fittingly enough,
towel to “absorb” the water. But that is not the same. The called the electromagnetic spectrum), one or the other
water molecules are still completely intact, they have of these quantities is preferred. My favorite AM sports
just bonded with the particles in the towel. Then you radio station when I was growing up broadcasted using
simply move them somewhere else, by either throwing light at 660 kHz (frequency); I heated up my coffee in
them into the trash or wringing them down the drain. the microwave this morning with light at 2.45 GHz
With light, though, the story is different. Light comes (also frequency); but my favorite color is 450 nm (wave-
into an interaction, but does not come out. So what is length of blue light). Indeed these are all just different
light and how can this be explained? colors of light; the human eye only evolved to contain

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