Page 24 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
from around 650 to 780 nm, which is red. This is an example of a broadband light with a ‘width’ of 130 nm. IPL systems work in a similar fashion (watch this animation).
Filtered Light
● We know that most light consists of a range of wavelengths (colours). When required, we can apply filters to ‘remove’ some of those wavelengths. In the example below, a red filter is used to ‘subtract’ out the blue, yellow and green light falling on it. The only light that gets through is red! That’s how filters work. Click here for a video of this process.
White Light =
        All the colours (photons) except the red ones are absorbed (subtracted) by the object
Figure 5: When white light falls on an object the atoms within the object absorb various wavelengths, depending on the chemistry. Any wavelengths which are not absorbed are reflected back into the environment – this is the ‘colour’ that we see. Absorption is essentially a ‘subtraction’ process.
The Colour of objects – Why is a blue object, blue?
● The light we see coming from any object is the light which is not absorbed by that object (click here for a video). Absorption is essentially a ‘subtraction’ process!
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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Absorbing object

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