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I have an object with incident light rays traveling away from this object. Some of these rays are traveling from the left-hand side through a simple lens (say, a double-convex converging lens). As these rays enter the lens, they are partially refracted, reflected, and absorbed. As these rays leave the lens, they are refracted even further, and eventually the light rays converge to a point (on a film screen or something).

Since the light rays are partially reflected and absorbed, wouldn't the light rays that entered the lens at the edges (where the lens is thinner) be less reflected/absorbed than the light rays that entered the lens near the center (where the lens is thicker)? If the light rays converged onto a film screen, would the differences in the intensity of light caused by these reflections/absorption (which can be traced back to differing thicknesses of the lens at different points) cause any issues with the images?

Would this ever need to be taken into an account by a scientist or student conducting an experiment involving data obtained from a camera?

Also, for a given convex lens (made of a particular material, and with a specific curvature), can the intensity of light as it reaches the focus point be thought of as a function of "vertical" distance from the center of the lens? This thought comes from the fact that this vertical distance would determine how much lens-material the light travels through. Are there examples of such functions, or is there a way of coming up with one for a simple lens?

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  • $\begingroup$ In most cases, this effect is minimal. In high-power experiments you might need to make sure that the amount of energy absorbed in the lens isn't enough to damage the lens. $\endgroup$ – The Photon Mar 15 '16 at 19:05
  • $\begingroup$ Yes, in technical optics the attenuation and, even more so, the reflection on the surfaces of optical elements are important. For a simple student experiment you are usually not required to care about it (it's unlikely that they are giving you access to a high power laser that can destroy lenses in the light path). The person(s) who designed your camera lens, on the other hand, did care about these effects. $\endgroup$ – CuriousOne Mar 15 '16 at 20:55
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Yes, you do have vignetting in camera, that cannot be pre-counteracted since it depends on the zoom. It can be seen when increasing the contrast. So for precise scientific measurement you would better account for this... And more generally totally calibrate your camera. Concerning the pixels intensity, this often consist at least to take an image of "black" (possibly averaged through multiple shot, to be substracted to measures) and an image of white (for normalization... and discarding dead pixels if any).

(see also optic geometric distortions).

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