Ok, so this is the key to understanding why measurement is distance independent. Irradiance falls by 1/r2 with distance and this is exactly compensated by larger spot sizes, which scale up by the same amount by which the irradiance decreases with distance. Thanks!
Let's assume you have an infinite plane with uniform temperature. The irradiance is constant with distance from this plane. However, when the device is closer it will get signal from a smaller spot, than when you move further away from the plane. Following this logic it should measure hotter and...
If irradiance is constant with distance and the device measures incident radiation from a cone, then a signal coming from larger distance should be larger since the spot diameter is larger there. What am I missing?
This sounds sensible to me. Except I can't imagine how then one of those things can cost only a couple of $.
Additionaly, in this datasheet it is stated that "As the temperature of the body rises, the
intensity of this infrared energy increases. The temperature of the body can therefore
be...
So, as far as I understand IR thermometer works by measuring light irradiance coming from an object (in the IR spectrum) and then calculating the object temperature using Stefan's law. Since the irradiance falls like 1/r2 with distance, I am wondering how it takes distance into consideration...
Ok, thanks. I have additional question.
The definition for the refractive index n= v/c is usually accompanied by the relation:
n = sqrt(epsilon)
where "epsilon" represents permittivity of the material. Should I suppose that by "permitivity" they mean its real part?
I'm asking this...
Refractive index is defined as
n = speed of light in a vacuum / speed of light in medium
Since both speed of light in a vacuum and speed of light in medium are real number, refractive index also has to be real. But we know that in general refractive index is complex. So what actually is...