Which of the following statements is not a characteristic of a plane progressive wave?

Analyze the question: We need the statement that is NOT a characteristic of a plane progressive wave.

Concept: A plane progressive (travelling) wave carries energy through a medium from one point to another. Its key features are:

• Energy is transported in the direction of travel (A is true).
• Every particle vibrates with the same amplitude, because no energy is lost in an ideal wave (C is true).
• Each particle vibrates with the same frequency and period, but at a different phase from its neighbours. The disturbance reaches each point at a slightly different time, so the phase changes along the wave (D is true).

Checking each option:

• A. Energy travels out through the medium. This is true, so it is not the answer.
• B. Neighbouring points have different amplitudes. This is false. In a progressive wave all particles have the same amplitude. (Different amplitudes along the medium is a feature of stationary waves, where nodes have zero amplitude and antinodes have maximum amplitude.)
• C. Neighbouring points have the same amplitude. This is true.
• D. Neighbouring particles vibrate with different phase. This is true.

Answer: B is the statement that is NOT a characteristic of a plane progressive wave.

Tip: Remember the contrast:

• Progressive wave: same amplitude everywhere, phase varies, energy is transported.
• Stationary wave: amplitude varies (nodes and antinodes), no net energy transport.

When a question says "not a characteristic", test each option against the true properties and pick the one that fails.