# What is the name of this equation? Seems to be from Optics

Should be a bright dot.
I think so too. But I re-tried the calculations; this time the object is located 40 meters from the front face of the lens, and the image is located 1.0256 meters from the back face of the lens.

This is different; it now becomes a bright dot. Now, I begin to question my method for calculating the diffraction pattern (each process within the method is valid, but I don't know if the series of methods is correct). Here is the process:

1. An object is at a certain distance ##z## from the lens. It propagates until to the front face of the lens by Fresnel Diffraction (the results of these method are considered valid).
2. The Fresnel Diffraction pattern (intensity) at the front face of the lens is multiplied by the thickness function, which results into the diffraction pattern (again, intensity) at the back face of the lens.
3. The diffraction pattern, now is the object, propagates from the back face of the lens to a certain distance to produce the image.

Are these steps correct?