Wavelength in standing waves equals twice the antinode spacing

Steps:

• In a standing wave on a string, nodes are zero-displacement points and antinodes are maximum-displacement points.
• The distance between adjacent nodes is λ/2, where λ is the wavelength.
• Similarly, the distance between adjacent antinodes is λ/2.
• Thus, double the distance between adjacent antinodes equals λ.

Why A is correct:

• By definition, adjacent antinodes are separated by half a wavelength, so doubling this distance yields the full wavelength λ.

Why the others are wrong:

• B: Distance between adjacent antinodes is λ/2, not λ.
• C: Distance between adjacent nodes is λ/2, so half of that is λ/4.
• D: Distance from a node to an adjacent antinode is λ/4.

Final answer: A