Double Slit Experiment

• https://javalab.org/en/double_slit_en/
• https://phet.colorado.edu/sims/html/wave-interference/latest/wave-interference_all.html

• Short notes: https://courses.lumenlearning.com/suny-physics/chapter/27-5-single-slit-diffraction/

• Wider the slits, lesser the intensity is spread, without affecting the fringe width (because most of the wavefronts from each slit move straight forward; see single slit version). There is a higher tendency to form fringes.

• The narrower the slits, the less the overall intensity too, because less light enters. To adjust for this, amplitude should be increased.
• But we can still see that the fringes start to go away, and the available intensity just gets spread out.
• Further apart the slits, the more fringes there are in the area where the intensity is spread (there will always be fringes as long as there are two slits; but
• Further apart the screen and the slits, the more the intesity is spread, but keeping the number of fringes the same, by increasing the fringe width.

Higher frequencies for a given slit width and position have the same effect as bringing the screen closer, which is the intensity is less spread out, and the fringes are more closer. In other words, for higher frequencies, since the wavelength is smaller, the intensity is more concentrated to the centre (because the cycles are less wider than the waves with higher wavelength, and hence spreads out lesser).

A similar observation is how cameras of smaller aperture have a wider FOV, but larger apertures have a smaller FOV, but intensity of light remains the same in both areas, giving the larger aperture more quality (but also the bokeh effect).