Power
Power and energy are closely related. Power is the rate at which energy is delivered, not an amount of energy itself.
Formula:
Power = Energy / Time 1 Watt = 1 Joule / Second
Terapeutic Energy = Power (Watts) or Joules/sec x Time (sec)
Power Density
Power density or Irradiance refers to the amount of power delivered per unit area.
Power density indicates the degree of concentration of the laser output
It is expressed in Watts per square centimeter (W/cm2),or miliWatts per square centimeter (mW/cm2)
Some studies have concluded that the power density may be of even greater signifcance than the dose.
Example: A laser’s output is 4 Watts, and it is illuminating a circle of 3 centimeter diameter
First fnd the area of the circle, 3.14 x 1.5 x 1.5 = 7 cm2
Then divide the power by the area, 4W / 7cm2 = 0.6 W/cm2
Formula: Irradiance (PD) =W/cm2
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donna@gigaalaser.com
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