What causes diffraction of waves around barriers?

Diffraction of waves around barriers is caused by the wave's interaction with the barrier, leading to a change in direction.

Diffraction is a fundamental characteristic of waves, including light, sound, and water waves. It is the phenomenon where waves bend, spread out, or change direction when they encounter an obstacle or opening that disrupts their path. This is a direct result of the wave's interaction with the barrier.

When a wave encounters a barrier, it interacts with the barrier's edges. This interaction causes the wave to bend around the barrier, leading to a change in direction. This bending is what we refer to as diffraction. The amount of diffraction (how much the wave bends) depends on the size of the barrier or opening and the wavelength of the wave. If the wavelength is much smaller than the barrier or opening, there will be less diffraction. Conversely, if the wavelength is comparable to or larger than the barrier or opening, there will be more diffraction.

For example, consider a water wave approaching a barrier with a small opening. As the wave reaches the barrier, the part of the wave that encounters the opening will continue to propagate forward, while the rest of the wave is blocked. The part of the wave that passes through the opening will then spread out in a semi-circular pattern on the other side of the barrier. This spreading out is the diffraction of the wave.

In the context of light waves, diffraction is responsible for the pattern of coloured fringes seen in a diffraction grating experiment. When light passes through a narrow slit or grating, it bends and interferes, creating a pattern of light and dark fringes on a screen. This is a direct demonstration of wave diffraction.

In summary, diffraction is a wave phenomenon that occurs when waves interact with barriers or openings. The interaction causes the waves to change direction and spread out, which is the essence of diffraction.