Which of the following are types of wave variations?

The correct answer is diffraction. This term refers to the bending of waves around obstacles and openings, which occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. Diffraction is a fundamental wave phenomenon observed in various types of waves, such as sound, light, and water waves.

Understanding diffraction is essential in fields such as physics and engineering, as it helps explain various behaviors of waves in real-world scenarios. For example, diffraction is why you can hear someone calling you from around a corner or why light spreads out when it passes through a narrow slit, leading to patterns of interference.

Other choices, such as trapping or retraction, do not represent recognized phenomena associated with wave variations in this context. Trapping might suggest capturing or holding waves, which is not a standard method for describing wave behavior, while retraction is more commonly associated with processes involving physical materials rather than with wave dynamics.