Using multiple slits of different widths in a diffraction experiment would produce a complex pattern, combining characteristics of both single-slit and multi-slit diffraction. Each slit width would contribute its own set of diffraction maxima and minima, leading to a superposition of different patterns on the screen. The narrower slits would produce wider diffraction maxima, while wider slits would result in narrower maxima. If the slits are close enough, their individual diffraction patterns would interfere with each other, creating a combined pattern that features characteristics of both diffraction and interference. This would result in a more intricate and varied fringe pattern, with variations in fringe width and intensity depending on the slit widths and their relative positions.

The fringes in a diffraction pattern become fainter as they move away from the centre due to the decrease in light intensity. In a single-slit diffraction experiment, the central maximum is the brightest because it receives the most light – being the point of constructive interference for the widest range of angles. As one moves away from the central maximum, the angles contributing to constructive interference decrease. This results in a decrease in the overall light intensity of each successive fringe. Additionally, the light waves are more spread out at larger angles, further diminishing the intensity of the outer fringes. The decrease in intensity is a physical manifestation of the energy distribution of the diffracted waves, confirming the wave nature of light.

Yes, diffraction patterns can be instrumental in determining the properties of the light source, particularly its wavelength. By analysing the diffraction pattern produced in experiments like the single or double-slit setup, the wavelength of light can be calculated. This is done by measuring the spacing between fringes in the pattern and using the known values of the slit width (or slit separation in the case of double-slit experiments) and the distance between the slits and the screen. The relationship between these measurements and the wavelength is governed by the diffraction equation. Hence, by carefully analysing the diffraction pattern and applying the appropriate mathematical relationships, one can accurately deduce the wavelength of the light used in the experiment.

The distance of the screen from the slit in a single-slit diffraction experiment significantly influences the diffraction pattern. As the distance increases, the diffraction pattern spreads out more, leading to a broader and more discernible pattern. This spreading occurs because, as the waves emanating from the slit travel further, they have more space to diverge before reaching the screen. Consequently, each fringe (both the central maximum and the subsequent maxima and minima) becomes wider and more separated from each other. Therefore, altering the screen distance is a practical way to study the details of the diffraction pattern, especially when observing the effects of slit width and wavelength on the pattern.

The coherence of the light source is pivotal in diffraction experiments. For clear and observable diffraction patterns, especially in double-slit experiments, the light source must be coherent. Coherent light waves have a constant phase difference, frequency, and waveform, leading to well-defined interference patterns. In single-slit experiments, coherence ensures a uniform diffraction pattern. In double-slit experiments, coherence is even more critical. Without it, the overlapping waves from the two slits would not produce a stable interference pattern, as their phase relationship would vary randomly. This would result in a smeared or non-existent fringe pattern, undermining the experiment's purpose of demonstrating wave interference and diffraction.