I‘m curios about the verification of the Huygens-Fresnel principle for light. For water it is clear visible in experiments, that the wave behind an opening disperses out all over 180°.
For light the same is claimed, like we see it in the sketch, I took from ad2004s answer to another question.
With naked eye, I‘m not able to see any light from very close to + an -90° from the obstacle with the slit. I’m curious about experimental results with sensitive enough instruments.
What you are describing is the diffraction pattern from a single slit as described in How can a single slit diffraction produce an interference pattern? The intensity as a function of angle is given by:
$$ I(\theta) = I_0 ~ \mathrm{sinc}^2 \left(\frac{d\pi\sin\theta}{\lambda}\right) $$
where $d$ is the slit width and $\lambda$ is the wavelength of the light.
To observe this yourself is quite hard as the intensity falls rapidly with angle unless the slit width is comparable to the wavelength. When I did the experiment as part of my physics practicals we used a laser in a darkroom. A Google image search will find you many examples of the diffraction pattern.
