Standing waves can only occur in a medium that iscontained.liquid.gas. two-dimensional.solid.

Understanding Standing Waves

Standing waves are a result of the interference of two waves traveling in opposite directions, leading to a stable wave pattern that does not move through the medium.

Medium of Propagation

1. Types of Waves: Standing waves can occur in various media as long as certain conditions are met. It's crucial to consider how waves travel in different states of matter.

2. Conditions for Standing Waves: For standing waves to form, the medium must have boundaries that can reflect the waves. This is commonly seen in physical systems where waves can bounce back.

Analysis of Options

1. Liquid: Standing waves can occur on the surface of liquids (like water waves), particularly in bounded systems.

2. Gas: While gases can carry sound waves, they generally do not produce standing waves in the same way due to the absence of fixed boundaries.

3. Two-dimensional: This term is more related to the nature of the waves rather than the medium. Standing waves are a characteristic feature of physical dimensions.

4. Solid: Solids can easily form standing waves due to their rigid structure, allowing waves to reflect efficiently at the boundaries.

Final Answer

Standing waves can occur in a solid medium, where reflection at the boundaries can establish the conditions necessary for standing wave formation.