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How will detect the Wavelength of Infrared Light

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baba786

New Member
When we work on the Infrared Lights then we know that they are not visible with the normal human eyes. Because It start in the EMR spectrum after the visible region. But we know that there are many IR light source in Electronics component we used basically IR LED'S as well as IR Lasers Also .

MY QUESTION: I have an Infrared Led and as we know that Infrared Light follow the reflection,refraction so when I put Infrared Led's light such kind of materials those Follow the Total Internal reflection then IR light remains inside the Material(those follows the Total internal reflection : Acrylic).

Now I want to know that what will be the wave length of the IR light so it remains inside the Material now should come outside it .


I have an IR led's those have 1.5-2.5 working Voltage and want to glow them inside the Acrylic those have size

Length:87cm
width:5mm
width:50cm
Now TELL me what will be the wave length of the IR led's to glow all the acrylic I will glow the acrylic from the Length(87cm)side
 

Sceadwian

Banned
I'm not sure I follow the post. IR light won't suddenly be changed in wavelength so much that it will emit visible light no matter what you do.
 

baba786

New Member
suppose I have two leds of same working voltage but different wave length
now want to glow the acrylic material those has size
Length:90cm
Width of acrylic:5mm
height:50cm
now want to glow the acrylic completely from the length side
led1: working voltage 1.5to 2.5 voltage and wave length 850nm
led2:working voltage 1.5 to 2.5 voltage and wave length 900 nm
Now which leds I should prefer
 

duffy

Well-Known Member
Neither make any difference. Acrylic is transparent to IR. The critical angle formula doesn't have a wavelength term.

You want to look up "light pipes" and do raytracing.
 

duffy

Well-Known Member
What part of "acrylic is transparent to IR" don't you understand?
 

baba786

New Member
I will put the light inside the acrylic from its side length(87cm) that is rough and remaining all the part of the acrylic is transparent
 

duffy

Well-Known Member
Oh, no - "transparent" here means the acrylic itself will pass the infrared, in a range well above and below the wavelengths you listed. What you are referring to would be "smooth".

If the surface is "rough", you can have issues with "specular reflectivity". Specular reflections depend on the minimum feature size of the surface irregularities being smaller than the wavelength of the light.

It would help if you post a diagram of what you are trying to do.
 
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Willbe

New Member
Does the refractive index for IR in acrylic vary with frequency?
 
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