Could you please explain anti-nodals and nodals in relation to two-point interference?
Nodes are where a peak and a trough of two different ways meet up and add together to have a zero amplitude wave aka a NO (de) wave which you will see as a flat part of the wave in a water diffraction pattern or if you are experiencing sound waves as a ‘dead spot’ in the sound pattern (think back to announcers at your school sports days).
Anti nodes are where two peaks or two troughs meet up and create a wave that is the size of the two waves added up together e.g. a really loud spot at the sports day or a really big wave in the water diffraction pattern.
In these sorts of questions the path difference eg. one wave is 2 wavelengths and the other wave is 3 wavelengths so the path difference is 1 wavelength is important. If the path difference is a whole wavelength you have constructive interference happening and if the path difference is a half wavelength you have destructive interference happening.