Which type of waves are light waves?

Concept

Waves can be classified on more than one independent basis. Transverse and longitudinal describe the direction of oscillation relative to propagation, while electromagnetic describes a wave’s physical nature. In free space, the electric and magnetic fields of an electromagnetic wave oscillate perpendicular to the direction of travel.

Application

1. Visible light is electromagnetic radiation: it consists of coupled, time-varying electric and magnetic fields and does not require a material medium.

2. In free space, both fields are perpendicular to the direction in which the wave travels, so light also has transverse character.

3. Therefore, two listed descriptions apply to light simultaneously: transverse waves and electromagnetic waves.

Cross-check and contrast

• A longitudinal wave has oscillations parallel to propagation and is commonly represented by compressions and rarefactions; this is not the field geometry of light in free space.

• The set-level response “None of the above” is excluded because two individual classifications do apply.

Hence the applicable response is “More than one of the above.”