# Intensity with distance of LED

## Main Question or Discussion Point

Hi everyone,

I am trying to create a data file that contains the intensity of an LED at a particular distance. For each data segment, the distance from the centre point (red dot on my very amateur paint drawing) is d and the distance from the LED to this purple grid is z. So I calculated that the intensity at each point is:

(where power of LED is It=130mW to take an example)

I_data = It*$$\frac{z}{\sqrt{d^2 +z^2}}$$*z^(-2)

so I am just multiplying the intensity perpendicular to the grid by the cosine of the angle and the inverse of the distance squared.

The distance from the LED to the grid is around 15cm, so originally I had z=0.15, which gave me the wrong intensity values. So I am not sure what to try next, any help would be greatly appreciated!

As a side note, I would also like to use a lens to reduce the half power angle of the LED and I'm wondering how this would affect the code above.

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