Page 23 - Lasers and IPLs in Medical/Aesthetic Applications v1.2
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Chapter 1 – Fundamentals of Medical/Aesthetic Lasers and IPLs v1.2
 Long wavelengths = red colour
Short wavelengths = blue colour
Figure 4: The visible spectrum
● For example, red light is typically around 625 to 780 nm, while blue light is around 380 to 485 nm. Infra-red light is beyond 780 nm and extends up to around 10,000 nm. Humans cannot see infra-red light but we can feel some of it as heat (learn more about light here).
● Visible light is designated into bands:
   Colour of Light Wavelength range
 Violet 380 nm to 415 nm
 Indigo 415 nm to 440 nm
 Blue 440 nm to 485 nm
 Cyan 485 nm to 500 nm
 Green 500 nm to 575 nm
 Yellow 575 nm to 596 nm
 Orange 596 nm to 625 nm
 Red 625 nm to 780 nm
Monochromatic and broadband light
● Lasers produce a very narrow range of wavelengths. This is known as monochromatic light although it is not strictly mono!
● A typical laser will yield a ‘central’ wavelength – typically physicists and engineers call this the fundamental wavelength. The fundamental is determined purely by the lasing medium – ruby creates a deep red fundamental of 694 nm while the Nd:YAG will generate an infra-red fundamental of 1064 nm. However, in reality, there is a small ‘spread’ of wavelengths around the fundamentals – typically around 2 to 5 nm depending on the lasing medium.
● Broadband light is the term used to explain a wider range of wavelengths. For example, ‘white’ light is broadband since it contains many wavelengths. However, a filtered spotlight in a theatre may exhibit a red light – this is created by using a red filter which stops all the colours of the white light bulb, except the red portion. This portion may be
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Chapter 1 LEVEL A Fundamentals of Lasers/IPLs
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