A textbook describes waves as having oscillations of different wavelengths in multiple planes - Edexcel - A-Level Physics - Question 6 - 2023 - Paper 2

To determine the type of wave being described, we need to analyze the key phrases in the question. The oscillations of the waves are stated to be in multiple planes, suggesting they oscillate in perpendicular directions.

Here are the options:

1. Stationary waves - These do not necessarily have oscillations in multiple planes as they are typically fixed in place with nodes and antinodes.

2. Longitudinal waves - In longitudinal waves, oscillations occur in the same direction as the wave travels, which does not fit the description of being perpendicular.

3. Polarised transverse waves - Polarised waves have oscillations in a single plane, which also does not match the multiple plane description.

4. Unpolarised transverse waves - These waves have oscillations that occur in multiple planes and are perpendicular to the direction of energy transfer. This matches the description given in the question.

Thus, the correct answer is D: unpolarised transverse waves.